JAMB UTME - Chemistry - 1991 | Green Bridge CBT

Question 1 Report

Which of the following are the products of the reaction between CH3COOH and CI2 in sunlight?

CICH2COOH + HCI Correct answer

CH3COCI + HOCI

CH3COOCI + HCI

CH3COCI + HO2

Answer Details

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Question 2 Report

A quantity of air was passed through a weighed amount of alkaline pyrogallol. An increase in the weight of the pyrogallol would result from the absorption of?

nitrogen

neon

argon

oxygen Correct answer

Answer Details

Alkaline pyrogallol is a substance used to absorb oxygen from the air. When air is passed through it, the oxygen in the air is absorbed by the pyrogallol, causing an increase in its weight. Therefore, the correct answer to the question is oxygen. Nitrogen, neon, and argon are all gases that are present in the air, but they do not react with pyrogallol in this way.

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Air

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Question 3 Report

Ethene when passed into concentrated H2SO4 is rapidly absorbed. The product is diluted with water and then warmed to produce?

ethanol Correct answer

diethyl ether

ethanal

diethyl sulphate

Answer Details

When ethene (C2H4) is passed into concentrated sulfuric acid (H2SO4), the ethene molecule gets protonated by H+ ions from the acid. This leads to the formation of a carbocation intermediate. Next, water is added to the carbocation to form an alcohol. In this case, since the product is being warmed, the most likely product formed is ethanol (C2H5OH). The reaction can be represented by the following equation: C2H4 + H2SO4 → C2H5OH Therefore, the correct option is "ethanol."

Read lesson note on Kinetic Theory Of Matter And Gas Laws (JAMB)

Read lesson note on Electrolysis (JAMB)

Read lesson note on Acids, Bases And Salts (Ghana Only) (WAEC)

Kinetic Theory Of Matter And Gas Laws

Electrolysis

Acids, Bases And Salts (Ghana Only)

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Question 4 Report

30cm3 of oxygen at 10 atmospheres pressure is placed in a 20 dm3 container. Calculate the new pressure if temperature is kept constant?

6.7 atm

15.0 atm Correct answer

60.0 atm

66. 0 atm

Answer Details

Read lesson note on Kinetic Theory Of Matter And Gas Laws (JAMB)

Kinetic Theory Of Matter And Gas Laws

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Question 5 Report

The appropriate test paper to use in the above experiment is moist

litmus psper

potassium heptaoxodichromate (IV) paper

lead (ll) trioxonitrate (V) paper Correct answer

universal indicator paper

Answer Details

Read lesson note on Acids, Bases And Salts (Ghana Only) (WAEC)

Acids, Bases And Salts (Ghana Only)

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Question 6 Report

50 cm3 of sulphur (IV) oxide, 800 cm3 of ammonia, 450 cm3 of hydrogen chloride, 1.0 cm3 of at 15°C. Which of the following is suitable for demonstrating the fountain experiment?

Sulphur (IV) oxide hydrogen chloride

Carbon (IV) oxide and amonia

Amonia and hydrogen chloride Correct answer

Carbon (IV) oxide and surphur (IV) oxide

Answer Details

The fountain experiment is a classic chemistry demonstration where a gas is produced in a container and bubbles up through a liquid, creating a "fountain" effect. To perform this experiment, you need a gas that is less dense than the liquid and can dissolve in it to form bubbles. Out of the given options, only ammonia and hydrogen chloride can dissolve in water to form bubbles that are less dense than the liquid, making them suitable for the fountain experiment. Carbon (IV) oxide and sulphur (IV) oxide do not dissolve in water to form bubbles, and sulphur (IV) oxide and hydrogen chloride may react with each other to produce a toxic gas, making them unsuitable for the fountain experiment. Therefore, option C, ammonia and hydrogen chloride, is the suitable choice for the fountain experiment.

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Kinetic Theory Of Matter And Gas Laws

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Question 7 Report

In two separate experiments, 0.36g and 0.71g of chlorine combined with a metal X to give Y and Z respectively. An analysis showed that Y and Z contain 0.20g and 0.40g of X respectively. The data above represents the law of ?

multiple proportion

conservation of mass

constant composition Correct answer

creciprocal proportion

Answer Details

0.36g of Cl combines with 0.2g of x

1g of Cl will combine with $\frac{1 \times 0.2}{0.32}$ = 0.56

0.71g of U combines with 0.49g of x

1g of U will combine with $\frac{1 \times 0.4}{71}$ = 0.56

Ratio 0.56 : 0.56 = 1:1

Read lesson note on Chemical Combination (JAMB)

Chemical Combination

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Question 8 Report

Oxygen gas can be prepared by heating?

ammonium trioxonitrate (V)

ammonium trioxonitrate (III)

ppotassium trioxonitrate (V) Correct answer

mamgamese (IV) oxide

Answer Details

Yes, oxygen gas can be prepared by heating certain compounds. One of the most common ways to obtain oxygen gas is by heating potassium trioxonitrate (V) or what is commonly known as potassium nitrate (KNO3). When potassium nitrate is heated, it undergoes a chemical reaction that produces oxygen gas and potassium oxide (K2O). The balanced chemical equation for this reaction is: 2KNO3(s) → 2KNO2(s) + O2(g) Therefore, by heating potassium nitrate, oxygen gas can be produced. The other compounds listed, such as ammonium trioxonitrate (V), ammonium trioxonitrate (III), and manganese (IV) oxide, do not produce oxygen gas when heated.

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Atomic Structure And Bonding

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Question 9 Report

MnO-4 + 8H+ + ne ? Mn++ + 4H2O. Which is the value of n in the reaction above?

5 Correct answer

Answer Details

MnO-4 + 8H+ + ne- ? Mn++ + 4H2O

Since Mn has 7 electrons on one side and 2 electrons on the other side. The value of ne- is 5.

Read lesson note on Kinetic Theory Of Matter And Gas Laws (JAMB)

Read lesson note on Redox Reactions (WAEC)

Kinetic Theory Of Matter And Gas Laws

Redox Reactions

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Question 10 Report

Which of the following statements is TRUE of the complete hydrolysis of a glycerine by sodium hygroxide?

3 moles of NaOH are required for each mole of glyceride Correct answer

3 moles of glycerol are produced

Only one mole of soap is formed

concentrated H2SO4 is essential for the completion of the reaction

Answer Details

Read lesson note on Acids, Bases And Salts (JAMB)

Acids, Bases And Salts

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Question 11 Report

1.1 g of CaCI2 dissolved in 50 cm3 of water caused a rise in temperature of3.4°C. The heat of reaction, ∆H for CaCI2 in kj per mole is?

(Ca = 40, CI = 35.5, specific heat of water is 4.18 jk-1

-71.1 Correct answer

-4.18

+71.1

+111.0

Answer Details

This is a problem in thermodynamics that involves the calculation of the heat of reaction (∆H) for the dissolution of CaCl2 in water. The equation for the dissolution reaction is: CaCl2 (s) + H2O (l) → Ca2+ (aq) + 2Cl- (aq) The given information is: mass of CaCl2 = 1.1 g, volume of water = 50 cm3, temperature rise = 3.4°C, specific heat of water = 4.18 J K-1 g-1, and atomic weights of Ca and Cl are 40 and 35.5, respectively. To calculate ∆H, we need to use the equation: ∆H = -q / n where q is the heat absorbed by the solution (water + CaCl2), and n is the number of moles of CaCl2 dissolved. First, we need to calculate the number of moles of CaCl2: n = mass / molar mass n = 1.1 g / (40 g/mol + 2 x 35.5 g/mol) = 0.010 mol Next, we need to calculate the heat absorbed by the solution: q = m x c x ΔT where m is the mass of the solution, c is the specific heat of the solution, and ΔT is the temperature rise. The mass of the solution can be calculated from the density of water: density = mass / volume mass = density x volume mass = 1 g/cm3 x 50 cm3 = 50 g Now we can calculate q: q = 50 g x 4.18 J K-1 g-1 x 3.4°C = 714 J Finally, we can calculate ∆H: ∆H = -714 J / 0.010 mol = -71.4 kJ/mol Therefore, the answer is -71.1 kJ, which is closest to.

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Kinetic Theory Of Matter And Gas Laws

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Question 12 Report

A certain liquid has a high boiling point. It is viscous, non-toxic, miscible with water being very hygroscopic. This liquid is most likely to be?

CH3CH2CH2HO

CH3CHOHCH3

CH3CH2CHOHCH3

CH2OHCHOHCH2OH Correct answer

Answer Details

The liquid described as having a high boiling point, being viscous, non-toxic, miscible with water, and very hygroscopic is most likely to be which is CH2OHCHOHCH2OH. The key characteristics of the liquid can help us identify its chemical structure. A high boiling point indicates that the liquid has strong intermolecular forces, which are likely to be due to the presence of hydrogen bonds. Viscosity is also related to intermolecular forces; a highly viscous liquid indicates strong forces between its molecules. The liquid is also described as being miscible with water, meaning that it can mix with water in any proportion. This property suggests that the liquid contains polar groups that can form hydrogen bonds with water molecules. Additionally, the liquid is hygroscopic, which means that it has a strong affinity for water and can absorb moisture from the air. This property further supports the presence of polar groups in the liquid. By looking at the chemical structures of the options, we can see that only CH2OHCHOHCH2OH, contains multiple hydroxyl (-OH) groups, which are highly polar and capable of forming hydrogen bonds with water molecules. These hydroxyl groups also contribute to the liquid's high boiling point and viscosity, as they can form intermolecular hydrogen bonds with other molecules of the liquid. Therefore, based on the given properties and chemical structures of the options, we can conclude that the liquid in question is most likely to be CH2OHCHOHCH2OH.

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Acids, Bases And Salts

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Question 13 Report

A sample of a gas exerts a pressure of 8.2 atm when confined in a 2.93 dm3 container at 20°C. The number of moles of gas in the sample is?

(R = 0.082 litre atm / deg mole)

1.00 Correct answer

2.00

3.00

4.00

Answer Details

PV = nRT
2.93 x 8.2 = 0.082 x 293 xn
∴ n = (2.93 x8.2) / (0.082 x 293)
n = 1

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Kinetic Theory Of Matter And Gas Laws

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Question 14 Report

The electronic configuration of an elements is 1s22s22p63s23p3. How many unpaired electrons are there in the element?

3 Correct answer

Answer Details

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Structure Of The Atom

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Question 15 Report

The solubility of copper (II) tetraoxosulphate (Iv) is 75g in 100g of water at 100°C and 25g in 100g of water at 30°C. What mass of the salt would crystallize, if 50g of copper (II) tetraoxosulphate (VI) solution saturated at 100°C were cooled to 30°C ?

57.5

42.2

28.6

14.3 Correct answer

Answer Details

The solubility of copper (II) tetraoxosulphate (IV) is given as 75g in 100g of water at 100°C and 25g in 100g of water at 30°C. This means that at 100°C, 100g of water can dissolve up to 75g of the salt while at 30°C, 100g of water can dissolve up to 25g of the salt. If 50g of copper (II) tetraoxosulphate (VI) solution saturated at 100°C were cooled to 30°C, some of the salt would crystallize out since the solubility of the salt in water decreases as the temperature decreases. First, we need to find out how much of the salt is already dissolved in the 50g solution. At 100°C, 100g of water can dissolve 75g of the salt. Therefore, in 50g of water, we can dissolve: (75g/100g) x 50g = 37.5g of copper (II) tetraoxosulphate (IV) This means that 37.5g of the salt is already dissolved in the 50g solution at 100°C. When the solution is cooled to 30°C, the solubility of the salt reduces to 25g/100g of water. This means that the maximum amount of salt that can be dissolved in 50g of water at 30°C is: (25g/100g) x 50g = 12.5g of copper (II) tetraoxosulphate (IV) Therefore, the amount of salt that would crystallize out is the difference between the amount of salt already dissolved in the solution and the maximum amount of salt that can be dissolved in the solution at 30°C: 37.5g - 12.5g = 25g So, 25g of copper (II) tetraoxosulphate (IV) would crystallize out when 50g of the saturated solution at 100°C is cooled to 30°C. Therefore, the answer is 14.3g.

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Solubility

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Question 16 Report

Calculate the volume of carbon (IV)oxide measured at s.t.p, produced when 1 kg of potassium hydrogen trioxocarbonate (IV) is totally decomposed by heat?(G.M.V. at s.t.p 22.4 dm3, K = 39, O = 16, C = 12, H = 1)

28 dm3

56 dm3

112 dm3 Correct answer

196 dm3

Answer Details

The question is asking for the volume of carbon dioxide produced when 1 kg of potassium hydrogen trioxocarbonate (IV) is decomposed at standard temperature and pressure (STP). We can start by writing the balanced chemical equation for the decomposition of potassium hydrogen trioxocarbonate (IV): 2KHCO3(s) → K2CO3(s) + H2O(g) + CO2(g) From this equation, we see that for every 2 moles of potassium hydrogen trioxocarbonate (IV) decomposed, 1 mole of carbon dioxide is produced. The molar mass of KHCO3 is: 1(39) + 1(12) + 3(16) = 100 g/mol Therefore, 1 kg (1000 g) of KHCO3 is equal to: 1000 g / 100 g/mol = 10 mol Since 2 moles of KHCO3 produce 1 mole of CO2, the number of moles of CO2 produced is: 10 mol / 2 = 5 mol At STP, 1 mole of any ideal gas occupies 22.4 dm^3. Therefore, the volume of CO2 produced is: 5 mol x 22.4 dm^3/mol = 112 dm^3 So the answer is 112 dm^3. Therefore, the correct option is: - 112 dm^3

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Stoichiometry And Chemical Reactions

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Question 17 Report

Which of the following can be obtained by fractional distillation?

Nitrogen from liquid air Correct answer

Sodium chloride from sea water

Iodine from a solution of Iondine in carbon tetrachloride

Sulphur from a solution of sulphur incarbon disulphide

Answer Details

Fractional distillation is a process used to separate a mixture of different substances with different boiling points. The substance with the lowest boiling point will vaporize first and can be collected as a separate fraction. By repeating the process, each component of the mixture can be obtained in a separate fraction. Out of the given options, nitrogen from liquid air can be obtained by fractional distillation because liquid air is a mixture of nitrogen, oxygen, and other gases, and they have different boiling points. By fractional distillation, nitrogen can be separated from the mixture. Sodium chloride from seawater, iodine from a solution of iodine in carbon tetrachloride, and sulfur from a solution of sulfur in carbon disulfide cannot be obtained by fractional distillation because they are not mixtures of substances with different boiling points. Sodium chloride is a compound, and iodine and sulfur are elements. To obtain them, other methods such as precipitation, filtration, or chemical reactions would be necessary.

Read lesson note on Separation Of Mixtures And Purification Of Chemical Substances (JAMB)

Separation Of Mixtures And Purification Of Chemical Substances

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Question 18 Report

How many structural isomers can be written for the alkyl bromide, C4H9Br?

4 Correct answer

Answer Details

Read lesson note on Chemistry Of Carbon Compounds (Nigeria Only) (WAEC)

Chemistry Of Carbon Compounds (Nigeria Only)

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Question 19 Report

Copper (II) tetraoxosulphate (IV) is widely used as a?

fertilizer

fungicide Correct answer

disinfectant

purifier

Answer Details

Copper (II) tetraoxosulphate (IV) is widely used as a fungicide. It is effective against a range of fungal infections in plants, including powdery mildew, downy mildew, and black spot. It works by disrupting the cell membranes of the fungi, leading to their death. In addition to its use in agriculture, copper (II) tetraoxosulphate (IV) is also used in the production of various chemicals and as a pigment in ceramics and glass.

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Acids, Bases And Salts

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Question 20 Report

A given quantity of a gas occupies a volume of 228 cm3 at a pressure of 750mm Hg. What will be its volume at atmospheric pressure?

220 cm3

225 cm3 Correct answer

230 cm3

235 cm3

Answer Details

We can use the combined gas law to solve this problem, which states that the product of pressure and volume is directly proportional to the product of the number of moles of gas and the absolute temperature. Since the number of moles of gas and the temperature are constant, we can use the following equation: P1V1 = P2V2 where P1 is the initial pressure, V1 is the initial volume, P2 is the final pressure (atmospheric pressure), and V2 is the final volume (what we want to find). Substituting the values given in the problem, we get: (750 mm Hg)(228 cm^3) = (760 mm Hg)(V2) Solving for V2, we get: V2 = (750 mm Hg)(228 cm^3) / (760 mm Hg) V2 = 225 cm^3 Therefore, the volume of the gas at atmospheric pressure would be 225 cm^3. The answer is option (B).

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Kinetic Theory Of Matter And Gas Laws

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Question 21 Report

How many grams of bromine will be required to completely react with 10 g of propyne?(C = 12, H = 1, Br = 80)

20g

40g

60g

80g Correct answer

Answer Details

C3H4 + 2Br2 - C3Br4 + 2H2
(36 + 4) (4 X 80)
40 g of C3H4 reacts with 320 g of Br
10 " " will react with
(10)/(40) x (320) /(1) = 80g

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Stoichiometry And Chemical Reactions

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Question 22 Report

Which of the following, in clear solution, forms a white precipitate when carbon (IV) oxide is bubbled into it for a short time?

KOH

NaOH

Ca(OH)2 Correct answer

AI(OH)3

Answer Details

When carbon (IV) oxide is bubbled into a clear solution, it forms a white precipitate of calcium carbonate (CaCO3). Therefore, the correct answer is Ca(OH)2, which is calcium hydroxide.

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Acids, Bases And Salts

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Question 23 Report

Which of the following are mixtures?

i. Petroleum
ii. Rubber latex
iii. Vulcanizer's solution
iv. Carbon (II) sulphide

i, ii and iii Correct answer

i, ii and iv

i and ii only

i and iv

Answer Details

Read lesson note on Separation Of Mixtures And Purification Of Chemical Substances (JAMB)

Separation Of Mixtures And Purification Of Chemical Substances

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Question 24 Report

One advantages of detergents over soap is that detergents?

are easier to maufacture

foam more than soap

form soluble salts with hard water Correct answer

are able to deter germs more than soap

Answer Details

Detergents have an advantage over soap because they are able to form soluble salts with hard water. Hard water contains dissolved calcium and magnesium ions which react with soap to form insoluble scum. Detergents, on the other hand, are able to form soluble salts with these ions and do not react to form scum. This makes detergents more effective for cleaning in hard water areas. The other options listed do not accurately describe an advantage of detergents over soap.

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Acids, Bases And Salts

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Question 25 Report

Which of the following equimolar solutions, Na2CO3 Na2 SO

4CI FeCI3 CH3COONa,

Have pH greater than 7?

FeCI 3 and NH 4CI

Na2CO3, CH3COONa and Na,Na2SO4

Na2CO3 and CH3COONa Correct answer

FeCI3, CH3COONa and NH4CI

Answer Details

Read lesson note on Acids, Bases And Salts (Ghana Only) (WAEC)

Acids, Bases And Salts (Ghana Only)

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Question 26 Report

50 cm3 of sulphur (lV) oxide, 800 cm3 of carbon (IV) oxide will respectively saturate 1.0cm3 of water at 15oC. Which of the following is suitable for demonstrating the fountain experiment?

Sulphur (IV) oxide and hydrogen chloride.

Carbon (IV) oxide and ammonia

Ammonia and hydrogen chloride Correct answer

Carbon (IV) oxide and Sulphur (IV) oxide

Answer Details

Read lesson note on Acids, Bases And Salts (Ghana Only) (WAEC)

Acids, Bases And Salts (Ghana Only)

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Question 27 Report

The ions X- and Y+ are isoelectronic, each containing a total of 10 electrons.

How many protons are in the nuclei of the neutral atoms of X and Y respectively?

10 and 10

9 and 9

11 and 9

9 and 11 Correct answer

Answer Details

X- means one excess electron, hence 9 protons while Y +/- means one deficit electron hence 11 protons X and Y = 9 and 11

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Structure Of The Atom

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Question 28 Report

Atoms of element X (with 2 electrons in the outer shell). combine with atoms of Y (with 7 electrons in the outer shell).

Which of the following statements is FALSE? The compound formed

has formula XY Correct answer

is likely to be ionic

contains X2+ ions

contains Y- ions

Answer Details

The false statement is "contains X2+ ions". When atoms of X (with 2 electrons in the outer shell) combine with atoms of Y (with 7 electrons in the outer shell), they are likely to form an ionic bond. In this bond, the X atom loses 2 electrons to become a cation with a 2+ charge (X2+), and the Y atom gains one electron to become an anion with a 1- charge (Y-). Therefore, the compound formed contains Y- ions but not X2+ ions, making statement 3 false. The compound formed will have a formula of XY because the cation (X2+) and anion (Y-) combine in a 1:1 ratio to form an electrically neutral compound.

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Question 29 Report

Which of the following ions is a pollutant in drinking water even in trace amounts?

Ca2+

Hg2+ Correct answer

Mg2+

Fe2+

Answer Details

The pollutant in drinking water, even in trace amounts, among the given ions is Hg2+. Mercury (Hg) and its compounds are highly toxic and can cause serious health problems, including neurological and developmental damage, even at low concentrations. Therefore, the presence of mercury in drinking water can be harmful to human health. The other ions listed, Ca2+, Mg2+, and Fe2+, are essential minerals that are generally safe to consume in drinking water, and they do not pose a significant health risk in trace amounts.

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Acids, Bases And Salts

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Question 30 Report

Which of the following compounds can exist as geometric isomers?

2-methylbut-2ene

But-2-ene Correct answer

But-1-ene

CI-C-Br

Answer Details

Geometric isomers are compounds with the same molecular formula, the same connectivity of atoms, and different arrangements of their substituent atoms in space. For compounds to be able to exist as geometric isomers, they must have a carbon-carbon double bond or a carbon-carbon triple bond. In the options given, only 2-methylbut-2ene and but-2-ene have a carbon-carbon double bond, which means they can exist as geometric isomers. But-1-ene does not have a double bond, and CI-C-Br is not an organic compound and does not have a carbon-carbon bond, so they cannot exist as geometric isomers. Therefore, the answer is: - 2-methylbut-2ene - But-2-ene

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Question 31 Report

2H2S(g) + SO2(g) → 3S(s) + 2H2O(I). The above reaction is?

a redox reaction H2S is the oxidant and SO2 is the reductant

a redox reaction in which SO2 is the oxidant and H2S is the reductant Correct answer

not a redox reaction because there is no oxidant in reaction equation

not a redox because there is no reductant in the reaction equation

Answer Details

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Redox Reactions

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Question 32 Report

An iron ore is known to contain 70.0% Fe2O3. The obtain from 80kg of the ore is?(Fe = 56, O = 16)

35.0 kg

39.2 kg Correct answer

70.0 kg

78.4 kg

Answer Details

The given iron ore contains 70.0% Fe2O3, which means that for every 100 grams of the ore, 70 grams is Fe2O3 and 30 grams is other substances. We are asked to determine the amount of Fe obtained from 80 kg of the ore. To solve this problem, we need to first calculate the amount of Fe2O3 in 80 kg of the ore. Since the ore contains 70.0% Fe2O3, the amount of Fe2O3 in 80 kg of the ore is: 70.0% × 80 kg = 0.70 × 80 kg = 56 kg Next, we need to calculate the amount of Fe in 56 kg of Fe2O3. The molecular weight of Fe2O3 is: 2(Fe) + 3(O) = 2(56 g/mol) + 3(16 g/mol) = 160 g/mol This means that 1 mole of Fe2O3 contains 2 moles of Fe. Therefore, the number of moles of Fe in 56 kg of Fe2O3 is: (56 kg) / (160 g/mol) × (2 mol Fe / 1 mol Fe2O3) = 0.7 mol Fe Finally, we can calculate the amount of Fe in 80 kg of the ore by multiplying the number of moles of Fe by the molar mass of Fe: 0.7 mol Fe × 56 g/mol = 39.2 kg Therefore, the amount of Fe obtained from 80 kg of the ore is 39.2 kg. Hence, the correct answer is option (B) 39.2 kg.

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Stoichiometry And Chemical Reactions

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Question 33 Report

CH3-CH-CH3

CH2CI Is known as?

1-chloro-2-methylbutane

1-chloro-2-methylpropane Correct answer

2-chloromethylpropane

1-chloro-2, 2-dimethylethane

Answer Details

The first molecule is a three-carbon chain with two carboxylic acid functional groups attached to the first and second carbon atoms. The second molecule is a two-carbon chain with a chlorine atom attached to the first carbon atom. Using the IUPAC naming system, the name of the first molecule is "propanedioic acid" or "malonic acid" and the name of the second molecule is "1-chloro-2-methylpropane". Therefore, the answer is 1-chloro-2-methylpropane.

Read lesson note on Chemistry Of Carbon Compounds (Nigeria Only) (WAEC)

Chemistry Of Carbon Compounds (Nigeria Only)

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Question 34 Report

Which of the following metals can be prepared in samples by the thermal decomposition of their trioxonitrate (V) salts?

Copper and mercury

Silver and copper

Mercury and silver Correct answer

Magnesium and mercury

Answer Details

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Metals And Their Compounds

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Question 35 Report

Which of the following gases will rekindle a brightly glowing splint?

NO2

N2O Correct answer

CI2

Answer Details

The gas that will rekindle a brightly glowing splint is oxygen, which is present in N2O (nitrous oxide). When a glowing splint is introduced into a gas that contains oxygen, the oxygen reacts with the glowing ember and reignites the splint. This test is commonly used to identify the presence of oxygen in a gas mixture. Therefore, the correct answer is N2O.

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Kinetic Theory Of Matter And Gas Laws

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Question 36 Report

Addition of aqueous ammonia to a solution of Zn++ gives a white precipitate which dissolves in an excess of ammonia because?

zinc is amphoteric

zinc hydroxide is readily soluble

zinc forms a complex which is readily soluble in excess ammonia Correct answer

ammonia solution is a strong base

Answer Details

The addition of aqueous ammonia to a solution of Zn^++ gives a white precipitate of zinc hydroxide (Zn(OH)2), which dissolves in excess ammonia to form a colorless, water-soluble complex ion called tetraamminezinc(II) ([Zn(NH3)4]^(2+)). This happens because zinc hydroxide is an amphoteric substance, which means it can react as an acid or a base. In the presence of aqueous ammonia, it acts as an acid and forms the complex ion which is readily soluble in water. Therefore, the correct answer is "zinc forms a complex which is readily soluble in excess ammonia."

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Acids, Bases And Salts

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Question 37 Report

Which of the following salts can be melted without decomposition?

Na2CO3 Correct answer

CaCO3

MgCO3

ZnCO3

Answer Details

The salt that can be melted without decomposition is sodium carbonate (Na2CO3). This is because sodium carbonate has a high melting point and does not decompose at its melting point. On the other hand, calcium carbonate (CaCO3), magnesium carbonate (MgCO3), and zinc carbonate (ZnCO3) decompose upon melting due to the release of carbon dioxide (CO2) gas. Therefore, these salts cannot be melted without decomposition.

Read lesson note on Acids, Bases And Salts (Ghana Only) (WAEC)

Acids, Bases And Salts (Ghana Only)

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Question 38 Report

Which of the following equilibria is unaffected by a pressure change?

2NaCI(s) ↔ 2Na (I) + CI2(g)

H 2(g) + I2(g) ↔ 2HI(g) Correct answer

2O3(g) ↔ 3O2(g)

2NO2(g) ↔ N2O4(g)

Answer Details

Read lesson note on Chemical Kinetics And Equilibrium Systems (Ghana Only) (WAEC)

Chemical Kinetics And Equilibrium Systems (Ghana Only)

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Question 39 Report

If a current of 1.5 A is passed for 4.00 hours through a molten tin salt and 13.3g of tin is deposited, what is the oxidation state of the metal in the salt?(Sn = 118.7, F = 96500 C mol-1)

2 Correct answer

Answer Details

Q = It = 1.5 x 4 x 60 x 60
13.3 g = 216000 C
118.7 g = (216000 x118.7) / (13.3) = 1927759.4 C
06500 C - 1 mole
1927759.4 C = (1927759.4) / (96500) = 1.998 = 2

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Electrolysis

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Question 40 Report

Magnesium (IV) oxide is known to hasten the decomposition of hydrogen peroxide. Its main action is to?

increase the surface area of the reactants

increase the concntration of the reactants

lower the activation energy for the reaction Correct answer

lower the heat of reaction, ∆H, for the reaction

Answer Details

Magnesium (IV) oxide works as a catalyst in the decomposition of hydrogen peroxide, which means it helps speed up the reaction without getting used up in the process. The main action of the catalyst is to lower the activation energy for the reaction, making it easier for the reactants to overcome the energy barrier and react with each other. This makes the reaction occur more quickly than it would without the catalyst. Therefore, the correct option is: "lower the activation energy for the reaction".

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Rates Of Chemical Reaction

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Question 41 Report

NO(g) + CO(g) ↔ (1)/(2)N2(g) + CO2(g) ∆H = -89.3 kj.

What conditions would favour maximum conversion of nitrogen (II) oxide and carbon (II) oxide in the reaction above?

Low temperature and high pressure Correct answer

High temperature and low pressure

High temperature and high pressure

Low temperature and low pressure

Answer Details

The given reaction is exothermic, which means it releases heat when the reaction proceeds. According to Le Chatelier's principle, increasing the pressure and decreasing the temperature favors the reaction that produces fewer moles of gas. In this case, the reaction produces 2 moles of gas (N2 and CO2) from 2 moles of gas (NO and CO). So, decreasing the temperature and increasing the pressure will shift the equilibrium towards the side with fewer moles of gas, i.e., the forward reaction. Therefore, the conditions that would favor maximum conversion of nitrogen (II) oxide and carbon (II) oxide are low temperature and high pressure. Hence, the correct answer is: Low temperature and high pressure.

Read lesson note on Kinetic Theory Of Matter And Gas Laws (JAMB)

Kinetic Theory Of Matter And Gas Laws

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Question 42 Report

Which of these is an acid salt?

K2SO4-.AI2(SO4)3.24H2O

CuCO3.Cu(OH)2

NaHS Correct answer

CaOCI2-

Answer Details

Read lesson note on Acids, Bases And Salts (Ghana Only) (WAEC)

Acids, Bases And Salts (Ghana Only)

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Question 43 Report

What volume of CO2 at s.t.p would be obtained by reacting trioxocarbonate (IV) with excess acid?(G.M.V at s.t.p = 22.4 dm3)

2.240 cm 3

22.40 cm 3 Correct answer

224.0 cm 3

2240 cm 3

Answer Details

The balanced equation for the reaction between trioxocarbonate (IV) and an acid is: CO2(g) + 2H+(aq) → H2O(l) + CO2(g) From the equation, we can see that one mole of trioxocarbonate (IV) reacts with two moles of H+ to produce one mole of CO2. At standard temperature and pressure (STP), one mole of any gas occupies 22.4 dm3 (or 22,400 cm3). Since the question states that there is an excess of acid, we can assume that all the trioxocarbonate (IV) will react, meaning that we only need to consider the amount of CO2 produced from one mole of the compound. Therefore, the volume of CO2 at STP produced from one mole of trioxocarbonate (IV) is 22.4 dm3 (or 22,400 cm3). Therefore, the correct answer is option B: 22.40 cm3.

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Kinetic Theory Of Matter And Gas Laws

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Question 44 Report

Which of the following represents the type of bonding present in ammonium chloride molecule?

Ionic only

Covalent only

Ionic and dative covalent Correct answer

Dative covalent only

Answer Details

Ammonium chloride (NH4Cl) is a compound composed of positively charged ammonium ions (NH4+) and negatively charged chloride ions (Cl-). The type of bonding present in a molecule is determined by the difference in electronegativity between the atoms in the molecule. Electronegativity is the ability of an atom to attract electrons towards itself. In ammonium chloride, nitrogen (N) has a higher electronegativity than hydrogen (H), and chlorine (Cl) has a higher electronegativity than nitrogen. This means that the bonding between hydrogen and nitrogen is covalent, where the electrons are shared between the two atoms. However, the bonding between ammonium and chloride is ionic, where the ammonium ion (NH4+) donates its electron to the chloride ion (Cl-) to form an ionic bond. Therefore, the type of bonding present in ammonium chloride is ionic and covalent. "Ionic and dative covalent," is the correct choice.

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Chemical Combination

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Question 45 Report

A property of a colloidal dispersion which a solution does not have is?

the Tyndall effect Correct answer

homogeneity

osmotic pressure

surface polarity

Answer Details

A solution is a homogeneous mixture of two or more substances, while a colloidal dispersion is a heterogeneous mixture where particles are dispersed in a continuous medium. One property of a colloidal dispersion that a solution does not have is the Tyndall effect. The Tyndall effect is the scattering of light by colloidal particles, which makes the path of the light visible. In a solution, the particles are too small to scatter light, so the path of light is not visible. Homogeneity, osmotic pressure, and surface polarity are properties that both solutions and colloidal dispersions can have.

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Solubility

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Question 46 Report

The elections or two atoms Y and Z are arranged in shes as shown above. The bond formed between the atoms of Y and Z is

ionic

convalent Correct answer

dative

metallic

Answer Details

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Question 47 Report

A sample of temporary hard water can be prepared in the laboratory by?

disolving calcium chloride in distilled water

saturating lime water with carbon (IV) oxide Correct answer

saturating distilled water with calcium hydroxide

dissolving sodium hydrogen trioxocarbonate (IV) in some distilled water

Answer Details

Read lesson note on Acids, Bases And Salts (Ghana Only) (WAEC)

Acids, Bases And Salts (Ghana Only)

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Question 48 Report

The data in the table above shows the rate of reaction of nitrogen (ll) oxide with chlorine at 25oC It can be concluded that doubling the initial concentration of NO increase the rate of reaction by a factor of

two

three

four Correct answer

five

Answer Details

3.0 x 10-5 x 4 = 1.2 x 10-4
.: The rate increase by a factor of 4

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Rates Of Chemical Reaction

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Question 49 Report

Which of the following is arranged in order of increasing electronegativity?

Chlorine, aluminium, magnesium, phosphorus, sodium