WAEC SSCE - Chemistry - 2009 (Objective)

Energy Changes

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Question 3 Report

Which of the following alloys does not contain copper? l. Brass II. Bronze III. Steel

l only

ll only

lll only Correct answer

ll and lll only

Answer Details

Steel does not contain copper, so the correct answer is III only. Brass is an alloy of copper and zinc, and bronze is an alloy of copper and tin. Steel is an alloy of iron and carbon, and may also contain other elements such as manganese, nickel, and chromium.

Read lesson note on Non-metals And Their Compounds (JAMB)

Non-metals And Their Compounds

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Question 4 Report

Dry hydrogen chloride when dissolved in methylbenzene

turns blue litmus paper red

turns red litmus paper blue

does not affect litmus paper Correct answer

bleaches litmus paper

Answer Details

Dry hydrogen chloride gas (HCl) when dissolved in methylbenzene does not affect litmus paper. This is because methylbenzene is a non-polar solvent and does not contain water, which is required for litmus paper to change color. Therefore, litmus paper cannot be used to test the acidity or basicity of the solution.

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

Acids, Bases And Salts (Ghana Only)

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Question 5 Report

Which of the following molecules is not linear in shape?

CO₂

O ₂

NH₃ Correct answer

HCI

Answer Details

NH₃ is not linear in shape. It has a trigonal pyramidal shape because of the presence of one lone pair of electrons on the nitrogen atom. The other three bonded hydrogen atoms are at an angle of approximately 107 degrees to each other. CO₂, O₂, and HCl are all linear in shape.

Read lesson note on Atomic Structure And Bonding (JAMB)

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Question 6 Report

How many molecules are there in 14 g of nitrogen at s.t.p.? [N = 14, Avogadro's constant = 6.02 x 10²³ mol^-1]

6.02 x 10²³ Correct answer

3.01 x 10²³

8.43 x 10²⁴

1.20 x 10²⁴

Answer Details

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

Read lesson note on Stoichiometry And Chemical Reactions (WAEC)

Stoichiometry And Chemical Reactions

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Question 7 Report

Which of the following electronic configurations correctly represents an element in period 3 of the periodic table?

1s² 2s² 2p²

1s² 2s² 2p⁶

1s² 2s² 2p⁶ 3s² 3p⁴ Correct answer

1s² 2s² 2p⁶ 3s² 3p⁶ 4s¹

Answer Details

Period 3 of the periodic table includes the elements sodium (Na), magnesium (Mg), aluminum (Al), silicon (Si), phosphorus (P), sulfur (S), and chlorine (Cl). The correct electronic configuration for an element in period 3 should have 3 energy levels and electrons distributed among those energy levels according to the Aufbau principle. Looking at the options given: - represents an element in period 2 as it has only 2 energy levels. - represents the noble gas configuration of the element neon (Ne) in period 2. - represents an element in period 3 with 3 energy levels, where the outermost energy level has 6 electrons (3s² 3p⁴). This configuration is consistent with the element sulfur (S). - represents an element in period 4 as it has 4 energy levels. Therefore, the correct option representing an element in period 3 is with the electronic configuration 1s² 2s² 2p⁶ 3s² 3p⁴.

Read lesson note on Periodic Chemistry (Nigeria Only) (WAEC)

Periodic Chemistry (Nigeria Only)

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Question 8 Report

Consider the reaction represented by the equation: 2H₂SO _4(aq0 + C_(s) → 2H₂O_(l) + 2SO_2(g) + CO _2(g) H₂SO ₄ is acting as

a catalyst

an oxidizing agent Correct answer

a reducing agent

a sulphonating agent

Answer Details

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

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Question 9 Report

How many protons does ⁴⁰20Ca contain?

20 Correct answer

Answer Details

The atomic number of an element is defined as the number of protons in the nucleus of its atom. In the symbol ⁴⁰20_Ca, 20 is written as a subscript, which represents the atomic number of calcium. Therefore, the number of protons in the nucleus of ⁴⁰20_Ca is 20. Answer: 20.

Read lesson note on Atomic Structure And Bonding (JAMB)

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Question 10 Report

A consequence of global warming is

air pollution

flooding Correct answer

increased humidity

low rainfall

Answer Details

A consequence of global warming is flooding. Global warming causes the temperature of the earth to rise, leading to the melting of glaciers and ice caps, which increases the volume of water in the oceans. This increase in water level leads to flooding in low-lying areas and coastal regions. Additionally, global warming can cause more intense and frequent weather events, such as hurricanes and heavy rainfall, which can also lead to flooding.

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Environmental Pollution

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Question 11 Report

Consider the reaction represented by the equation: 2NaHCO₃ → Na₂CO ₃ + H ₂O + CO ₂. What is the mass of sodium trioxocarbonate (lV) produced by the complete decomposition of 33.6 g of sodium hydrogen trioxocarbonate (IV)? [NaHCO₃ = 84, Na₂CO₃ = 106]

10.6 g

16.8 g

21.2 g Correct answer

42.4 g

Answer Details

The balanced equation for the reaction shows that 2 moles of NaHCO₃ produce 1 mole of Na₂CO₃, and the molar mass of NaHCO₃ is 84 g/mol. Therefore, 84 g of NaHCO₃ will produce 106 g of Na₂CO₃. To determine the mass of Na₂CO₃ produced from 33.6 g of NaHCO₃, we need to use stoichiometry. 33.6 g NaHCO₃ x (1 mol NaHCO₃ / 84 g NaHCO₃) x (1 mol Na₂CO₃ / 2 mol NaHCO₃) x (106 g Na₂CO₃ / 1 mol Na₂CO₃) = 21.2 g Na₂CO₃ Therefore, the mass of sodium trioxocarbonate (lV) produced by the complete decomposition of 33.6 g of sodium hydrogen trioxocarbonate (IV) is 21.2 g. The correct answer is 21.2 g.

Read lesson note on Chemical Combination (JAMB)

Chemical Combination

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Question 12 Report

Which of the following compounds is not a double salt?

Zn(OH)NO₃ Correct answer

KAI(SO₄)₂

KCr(SO₄)₂

(NH₄)₂Fe(SO₄)₂

Answer Details

A double salt is a combination of two different salts which crystallize together to form a single substance with a unique formula. The formula of a double salt is a combination of the formulas of the two salts that make it up. From the given options, the compound that is not a double salt is Zn(OH)NO₃. This is because it does not contain two different salts that have crystallized together to form a new substance. Rather, it is a single compound containing the elements zinc, oxygen, nitrogen, and hydrogen. Therefore, the answer is: Zn(OH)NO₃

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

Acids, Bases And Salts

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Question 13 Report

The electron configuration of carbon atom in its excited state is [ ₆C]

1s²2s ²2px¹2py ¹

1s ² 2s ²2px ²2py^o

1s¹2s²2px¹2py¹2pz¹

1s ²2s¹2px¹2py¹2pz¹ Correct answer

Answer Details

The electron configuration of carbon in its ground state is 1s²2s²2p². This means that there are two electrons in the 1s orbital, two in the 2s orbital, and two in the 2p orbital. However, the question is asking about the excited state of carbon, which means that at least one electron has been promoted from a lower energy level to a higher energy level. In the case of carbon, one of the electrons in the 2s orbital is promoted to the 2p orbital, resulting in the electron configuration [ ₆C] 1s²2s¹2p³. Therefore, the correct answer is 1s²2s¹2px¹2py¹2pz¹.

Read lesson note on Atomic Structure And Bonding (JAMB)

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Question 14 Report

Which of the following expressions correctly represents Charles' law?

PV = K

R \(\alpha \frac{1}{\sqrt{p}\)

PV = RT

V = KT Correct answer

Answer Details

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

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Question 15 Report

In bonded atoms, increase in electronegativity difference,

increases polarity Correct answer

decreases polarity

has no effect on polarity

brings the polarity to zero

Answer Details

In bonded atoms, the electronegativity difference determines the distribution of electrons between the atoms. When there is an increase in the electronegativity difference between two atoms in a bond, one atom attracts electrons more strongly than the other, resulting in an uneven distribution of electrons. This uneven distribution of electrons leads to an increase in the polarity of the bond, as the atom that attracts electrons more strongly gains a partial negative charge, while the other atom gains a partial positive charge. Therefore, an increase in electronegativity difference increases the polarity of the bond.

Read lesson note on Oxidation And Reduction (JAMB)

Read lesson note on Periodic Chemistry (Ghana Only) (WAEC)

Oxidation And Reduction

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Question 16 Report

What is the product of the reaction between propene and 1 mole of hydrogen iodide?

CH₃CHICH₃ Correct answer

CH ₃CH₂CHI₂

CH ₃CH ₂CI₃

CH ₃CHICH₂I

Answer Details

The reaction between propene and 1 mole of hydrogen iodide results in the addition of the hydrogen iodide molecule to the carbon-carbon double bond in propene. The hydrogen atom adds to one carbon atom of the double bond, and the iodine atom adds to the other carbon atom. As a result, the product formed is CH ₃CHICH₃, which is 2-iodopropane. Therefore, the correct answer is: the product of the reaction between propene and 1 mole of hydrogen iodide is CH₃CHICH₃.

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

Chemistry Of Carbon Compounds (Nigeria Only)

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Question 17 Report

The electron configuration of carbon atom in its excited state is [ 6C]

1s²2s ²2px¹2py ¹

1s ² 2s ²2px ²2py^o

1s¹2s²2px¹2py¹2pz¹

1s ²2s¹2px¹2py¹2pz¹ Correct answer

Answer Details

The electron configuration of an atom describes the arrangement of electrons in its energy levels or orbitals. The notation [ 6C ] means that the excited carbon atom has six electrons in its outermost energy level, which is the second energy level (n=2). The correct electron configuration for a carbon atom in its excited state is 1s²2s¹2p². The notation [ 6C ] can be understood as follows: the normal electron configuration for carbon is 1s²2s²2p², meaning that it has four electrons in its outermost energy level. By exciting one of the 2s electrons to the empty 2p orbital, the atom now has a total of six electrons in the n=2 energy level, hence the notation [ 6C ]. Option D, 1s²2s¹2px¹2py¹2pz¹, represents the electron configuration of a carbon atom in its ground state.

Read lesson note on Atomic Structure And Bonding (JAMB)

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Question 18 Report

Which of the following acids from normal salt only?

Tetraoxosulphate (IV) acid

Tetraoxophosphate (V) acid

Trioxonitrate (V) acid Correct answer

Trioxosulphate (IV) acid

Answer Details

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

Read lesson note on Periodic Chemistry (Ghana Only) (WAEC)

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Question 19 Report

The major product in the solvay process is

NaOH

Na ₂CO ₃ Correct answer

NH ₃

H ₂SO₄

Answer Details

The Solvay process is a method of producing sodium carbonate (Na₂CO₃) from brine and ammonia (NH₃). The process involves reacting brine with ammonia to form ammonium chloride (NH₄Cl), which is then reacted with limestone (CaCO₃) to produce carbon dioxide (CO₂), water (H₂O), calcium chloride (CaCl₂), and ammonia. The carbon dioxide is then reacted with the remaining ammonia to produce ammonium bicarbonate (NH₄HCO₃), which is then heated to produce sodium carbonate (Na₂CO₃), water, and carbon dioxide. Thus, the major product in the Solvay process is Na₂CO₃.

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

Acids, Bases And Salts (Ghana Only)

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Question 20 Report

Which of the following elements exhibits the same chemical properties as the atom \(\frac{35}{17}\)X? An element with

atomic number 17 Correct answer

atomic number 18

mass number 35

mass number 52

Answer Details

The element with the symbol \(\frac{35}{17}\)X represents an atom of chlorine with 17 protons and 18 neutrons. Elements with the same number of protons have the same chemical properties. Therefore, the answer is (a) an element with atomic number 17, which is chlorine.

Read lesson note on Chemical Bonds (Nigeria Only) (WAEC)

Read lesson note on Structure Of The Atom (WAEC)

Chemical Bonds (Nigeria Only)

Structure Of The Atom

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Question 21 Report

The following properties are characteristics of transition elements except

formation of complex ions

fixed oxidation states Correct answer

formation of coloured compounds

catalytic abilities

Answer Details

The question is asking which of the given properties is NOT a characteristic of transition elements. Transition elements are a group of elements in the periodic table that have partially filled d orbitals. They have several unique properties, including the ability to form complex ions, form coloured compounds, and exhibit catalytic abilities. However, one property that is not typically associated with transition elements is fixed oxidation states. Unlike many other elements, transition elements can have multiple oxidation states and are not limited to one fixed state. Therefore, the correct answer to the question is "fixed oxidation states."

Read lesson note on Chemical Combination (JAMB)

Chemical Combination

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Question 22 Report

Which of the following raw materials is used in the plastic industry ?

Calcium

Ethene Correct answer

Hydrogen

Methane

Answer Details

Ethene is the raw material used in the plastic industry. Ethene, also known as ethylene, is a hydrocarbon with the formula C2H4. It is produced from the cracking of petroleum fractions or natural gas. Ethene is a monomer that can be polymerized to form polyethylene, which is a versatile plastic used in a wide range of applications, from packaging materials to toys and medical devices. Calcium, hydrogen, and methane are not typically used as raw materials in the plastic industry.

Read lesson note on Basic Biochemistry And Synthetic Polymers (WAEC)

Basic Biochemistry And Synthetic Polymers

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Question 23 Report

Which of the following factors will affect the rate of the reaction represented by the equation? 2HCI_(aq) + CaCO _3(s) → CaCI_2(aq) + H₂O _(I) + CO_2(g) l. Pressure ll. Concentration III. Nature of reactants IV. Temperature

l and ll only

ll, lll and IV only Correct answer

l, ll and lll only

l, ll, lll and IV

Answer Details

The rate of the reaction represented by the equation 2HCI(aq) + CaCO3(s) → CaCI2(aq) + H2O(I) + CO2(g) can be affected by various factors: - Pressure: Pressure affects the rate of a reaction only if there are gases involved in the reaction. In this reaction, CO2 is produced as a gas, so increasing the pressure will increase the rate of the reaction. - Concentration: Increasing the concentration of the reactants will increase the number of collisions between the reactant particles and thus increase the rate of the reaction. - Nature of reactants: The nature of the reactants can affect the rate of the reaction. For example, a reaction involving reactive metals like magnesium will proceed faster than a reaction involving less reactive metals like copper. - Temperature: Increasing the temperature will increase the kinetic energy of the particles, resulting in more collisions and thus increasing the rate of the reaction. Therefore, the factors that will affect the rate of this particular reaction are ll, lll, and IV.

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Rates Of Chemical Reaction

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Question 24 Report

Which of the following hydroxides will readily dissolved in water?

Cu(OH)₂

NaOH Correct answer

Pb(OH)₂

Zn(OH)₂

Answer Details

NaOH will readily dissolve in water. This is because it is a strong base and its ionic bonds with Na⁺ and OH^- are easily broken in the presence of water, allowing the ions to separate and become hydrated. In contrast, Cu(OH)₂, Pb(OH)₂, and Zn(OH)₂ are relatively insoluble in water, meaning that their ionic bonds are not easily broken and they do not readily dissociate into their constituent ions in water.

Read lesson note on Solubility Of Substances (Ghana Only) (WAEC)

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

Solubility Of Substances (Ghana Only)

Acids, Bases And Salts (Ghana Only)

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Question 25 Report

Which of the following scientists discovered the neutron?

Ernest Rutherford

J.J Thompson

James Chadwick Correct answer

R. A. M illikan

Answer Details

James Chadwick discovered the neutron. In the early 1930s, he conducted a series of experiments that led to the discovery of an uncharged subatomic particle within the nucleus of the atom. This particle was later identified as the neutron, which plays a critical role in nuclear reactions and the stability of the nucleus. Chadwick's discovery of the neutron earned him the Nobel Prize in Physics in 1935.

Read lesson note on Structure Of The Atom (WAEC)

Structure Of The Atom

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Question 26 Report

In a chemical reaction, ∆H is positive when

H _(product) >H _(reactant) Correct answer

H_(product) < H _(reactant)

H _(product) = H _(reactant)

H _(product) = Zero _(reactant)

Answer Details

Read lesson note on Energy Changes (JAMB)

Energy Changes

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Question 27 Report

A solution that contains as much solute as it can dissolve at a given temperature is said to be

concentrated

saturated Correct answer

supersaturated

unsaturated

Answer Details

A solution that contains as much solute as it can dissolve at a given temperature is said to be saturated. This means that no more solute can be dissolved in the solution without changing the temperature or pressure. Any additional solute added to a saturated solution will remain undissolved and settle at the bottom of the container. The saturation point is determined by the solubility of the solute in the solvent, which is the maximum amount of solute that can dissolve in a given amount of solvent at a given temperature and pressure.

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Read lesson note on Solubility Of Substances (Ghana Only) (WAEC)

Solubility

Solubility Of Substances (Ghana Only)

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Question 28 Report

A catalyst increases the rate of chemical reaction by

decreasing the temperature of the reaction

decreasing the activation energy of the reaction Correct answer

increasing the surface area of the reactants

decreasing the surface area of the products

Answer Details

A catalyst is a substance that increases the rate of a chemical reaction by providing an alternative reaction pathway with lower activation energy. Activation energy is the energy required to start a chemical reaction. By lowering the activation energy, a catalyst makes it easier for reactant molecules to react and form products. As a result, the reaction can occur more quickly, which increases the rate of the chemical reaction. Therefore, the correct option is "decreasing the activation energy of the reaction".

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

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Read lesson note on Structure Of The Atom (WAEC)

Electrolysis

Structure Of The Atom

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Question 29 Report

Which of the following elements has the electronic configuration:1s²2s²2p⁶3s²3p¹? [₁₁Na, ₁₃A1,
₁₄N,₁₆S]

Al Correct answer

Answer Details

Read lesson note on Atomic Structure And Bonding (JAMB)

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Question 30 Report

Which of the following noble gases has electronic structure similar to that of N in NH ₃? [\(\frac{14}{7}\)N]

₂He

₁₀Ne Correct answer

₁₈Ar

₃₆Kr

Answer Details

Read lesson note on Structure Of The Atom (WAEC)

Structure Of The Atom

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Question 31 Report

What is the percentage by weight of calcium in Ca(OCI)₂? [Ca = 40, Cl = 35.5, O = 16]

28.0% Correct answer

31.6%

43.8%

44.5%

Answer Details

Read lesson note on Chemical Combination (JAMB)

Chemical Combination

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Question 32 Report

If 100 atoms of element X contains 70 atoms of ⁹X and 30 atoms of ¹¹X, calculate the relative atomic mass of X

9.6 Correct answer

10.6

11.6

20.0

Answer Details

To calculate the relative atomic mass of X, we need to take into account the mass and abundance of each isotope of X. We know that element X has two isotopes: ⁹X and ¹¹X. To calculate the relative atomic mass of X, we can use the formula: Relative atomic mass of X = (mass of ⁹X x % abundance of ⁹X) + (mass of ¹¹X x % abundance of ¹¹X) / 100 Substituting the values we have, we get: Relative atomic mass of X = (9 x 70) + (11 x 30) / 100 Relative atomic mass of X = 630 + 330 / 100 Relative atomic mass of X = 9.6 Therefore, the relative atomic mass of X is 9.6.

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Question 33 Report

Salts that contain water of crystallization are said to be

anhydrous

deliquescent

efflorescent

hydrated Correct answer

Answer Details

Salts that contain water of crystallization are said to be hydrated. Water of crystallization is the water molecules that are tightly bound to the salt molecules in a crystal structure. These water molecules can be removed by heating or by exposing the salt to dry air. When the water is removed, the salt becomes anhydrous. The number of water molecules present in a hydrated salt is indicated by a dot followed by a number in the chemical formula. For example, CuSO4.5H2O is copper sulfate pentahydrate, which means it contains five molecules of water of crystallization.

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

Acids, Bases And Salts

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Question 34 Report

Which of the following properties of covalent compounds is not correct? They

are non-electrolytes

are mostly gaseous and volatile liquids

have low melting point

have high boiling points Correct answer

Answer Details

The correct option is "have high boiling points." Covalent compounds are formed by sharing of electrons between two non-metal atoms. These compounds generally have low melting and boiling points due to their weak intermolecular forces. They are mostly gaseous or volatile liquids. Covalent compounds also do not dissociate into ions in solution, and therefore they are non-electrolytes. However, some covalent compounds with strong intermolecular forces may have high boiling points.

Read lesson note on Rates Of Chemical Reaction (JAMB)

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Rates Of Chemical Reaction

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Question 35 Report

The product of the reaction between C ₂H₅OH and concentrated H₂SO ₄ at 170^oC is

(C₂H₅)₂SO₄

CH ₃CH ₂HSO ₄

(C₂H₅)₂O

CH₂ = CH ₂ Correct answer

Answer Details

Read lesson note on Periodic Chemistry (Ghana Only) (WAEC)

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Question 36 Report

Which of the following arrangements is in order of increasing ionization energy?

AI, Si, P, S Correct answer

Si, AI,S,P

S,P,Si,AI

P, Si,S,AI

Answer Details

Read lesson note on Atomic Structure And Bonding (JAMB)

Read lesson note on Periodic Chemistry (Nigeria Only) (WAEC)

Periodic Chemistry (Nigeria Only)

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Question 37 Report

Which of the following substances is the anode in the dry Leclanche cell ?

Carbon rod

Muslin bag

The seal

Zinc container Correct answer

Answer Details

In a dry Leclanche cell, the anode is the negative electrode that releases electrons into the external circuit during the cell's discharge. The anode of a dry Leclanche cell is the zinc container. It acts as the negative terminal of the cell and is where the oxidation of zinc metal to zinc ions takes place, producing electrons and zinc ions which move towards the cathode. Therefore, the correct option is zinc container.

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Rates Of Chemical Reaction

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Question 38 Report

Which of the following ions is isoelectronic with neon? [₃Li, _{3F, ₁₀Ne, ₁₇CI,₁₉K]}

CI^-

F^- Correct answer

K⁺

Li,⁺

Answer Details

The question is asking which of the given ions has the same electronic configuration as neon. Neon is a noble gas and has an electronic configuration of 1s²2s²2p⁶. Isoelectronic refers to ions or atoms that have the same number of electrons, thus the same electronic configuration. Among the given options, the ion that has the same number of electrons as neon is the one that has 10 electrons in total. Looking at the options, the only ion with 10 electrons is F^-. Therefore, F^- is isoelectronic with neon. Therefore, the correct option is F^-.

Read lesson note on Structure Of The Atom (WAEC)

Structure Of The Atom

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Question 39 Report

How many orbitals are associated with the p-sub energy level?

3 Correct answer

Answer Details

The p-sub energy level has a total of three orbitals. These orbitals are represented as Px, Py, and Pz. Each orbital can hold a maximum of two electrons, and together they can hold a total of six electrons. Therefore, the correct answer is 3.

Read lesson note on Atomic Structure And Bonding (JAMB)

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Question 40 Report

The separation of petroleum fractions depends on the differences in their

boiling points Correct answer

molar masses

melting point

solubilities

Answer Details

The separation of petroleum fractions is based on their boiling points. The different fractions of petroleum are separated by a process called fractional distillation, where crude oil is heated and vaporized. As the vapor rises through a column, it gradually cools down. As it cools, the vapor condenses into a liquid, and the different fractions with different boiling points condense at different levels in the column. The lighter fractions with lower boiling points, such as gases and liquids like gasoline, condense at the top of the column, while the heavier fractions with higher boiling points, such as liquids like diesel and lubricating oil, condense at lower levels. Thus, the separation of petroleum fractions is dependent on the differences in their boiling points.

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 41 Report

Which of the statements about the behaviour of the atom is correct?

atomic size decreases down the group

atomic size increases across the period

anions are smaller than the parent atom

cations are smaller than the parent atom Correct answer

Answer Details

The correct statement about the behavior of the atom is that cations are smaller than the parent atom. When an atom loses one or more electrons to form a cation, the number of electrons is less than the number of protons, resulting in a net positive charge. This positive charge attracts the remaining electrons more strongly towards the nucleus, causing the atomic radius to decrease. Therefore, cations are smaller than their parent atoms. Conversely, when an atom gains one or more electrons to form an anion, the negative charge causes the electron cloud to expand, resulting in a larger atomic radius than the parent atom. Hence, the other options are incorrect.

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Structure Of The Atom

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Question 42 Report

Which of the following dilute acids does not react with metals to liberate hydrogen?

CH₃COOH_(aq)

HCI_(aq)

H₂SO_4(aq)

HNO_3(aq) Correct answer

Answer Details

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

Acids, Bases And Salts

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Question 43 Report

Ethanol reacts with excess acidified K₂Cr ₂O₇ to produce

ethanal

ethane

ethanoic acid Correct answer

ethylethanoate

Answer Details

Ethanol reacts with excess acidified K₂Cr ₂O₇ to produce ethanoic acid. This reaction is an oxidation reaction, where ethanol is oxidized to ethanoic acid. The K₂Cr ₂O₇ acts as an oxidizing agent and converts the ethanol to ethanoic acid by removing hydrogen atoms from ethanol and adding oxygen atoms to form a carboxylic acid. The other options listed in the question are not produced in this reaction.

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

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Energy Changes

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Question 44 Report

The number of particles in one mole of a chemical compound is the

atomic number

avogadro's number Correct answer

mass number

oxidation number

Answer Details

The number of particles in one mole of a chemical compound is called Avogadro's number. Avogadro's number is a constant that represents the number of particles (such as atoms, molecules, or ions) in one mole of a substance, which is approximately 6.02 x 10^23 particles. This number is used to convert between the number of moles of a substance and the number of particles it contains. For example, one mole of water contains 6.02 x 10^23 water molecules. Therefore, Avogadro's number is the correct option.

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Structure Of The Atom

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Question 45 Report

What is the molecular formula of a compound with empirical CH₂O and vapour density of 90? [H = 1, C = 12, O = 16]

C₄H₈O ₂

C₄H ₈O₃

C₆H₁₀C₅

C₆H₁₂O₆ Correct answer

Answer Details

Read lesson note on Periodic Chemistry (Ghana Only) (WAEC)

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Question 46 Report

When protein is heated to a high temperature it undergoes

condensation

denaturation Correct answer

hydrolysis

polymerization

Answer Details

When proteins are heated to high temperatures, they undergo denaturation. Denaturation is the process by which a protein loses its three-dimensional structure, which is critical to its function. This change in structure is due to the breaking of the weak bonds holding the protein together, such as hydrogen bonds, ionic bonds, and hydrophobic interactions. The loss of these bonds causes the protein to unfold and lose its specific shape, which can lead to a loss of function. Denaturation can also be caused by other factors such as changes in pH, exposure to detergents or solvents, or high pressure.

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

Read lesson note on Basic Biochemistry And Synthetic Polymers (WAEC)

Basic Biochemistry And Synthetic Polymers

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Question 47 Report

An important medical use of nuclear radiations is

activation analysis

carbon dating

radiotherapy Correct answer

tissue regeneration

Answer Details

One important medical use of nuclear radiations is radiotherapy. Radiotherapy uses high-energy radiation to destroy cancer cells and shrink tumors. This type of treatment is usually delivered by a machine called a linear accelerator, which produces high-energy X-rays or gamma rays that are directed towards the tumor. The radiation damages the DNA of the cancer cells, causing them to die. Radiotherapy is often used in combination with other treatments such as chemotherapy and surgery, and can be effective in treating a range of cancers including lung, breast, prostate, and brain cancer.

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Oxidation And Reduction

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Question 48 Report

Consider the reaction represented by the equation: ²³⁸₉₂U + ¹₀ → ¹³⁹ ₅₆Ba + ⁹⁴ ₃₆Kr + 3¹ ₀n. The reaction represents a

nuclear fission Correct answer

nuclear fusion

radioactive decay

spontaneous disintegration

Answer Details

The reaction shown in the equation ²³⁸₉₂U + ¹₀ → ¹³⁹ ₅₆Ba + ⁹⁴ ₃₆Kr + 3¹ ₀n represents nuclear fission. Nuclear fission is a process in which a heavy nucleus is split into two or more smaller nuclei and typically releases a large amount of energy in the form of heat and radiation. In this particular reaction, uranium-238 is bombarded with a neutron, which causes it to split into two smaller nuclei (barium-139 and krypton-94) and three neutrons. This process also releases a significant amount of energy in the form of radiation.

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Question 49 Report

An element Q forms a compound QCI₅. In which group of the periodic table is Q?

lll

V Correct answer

VII

Answer Details

The Roman numeral in the compound QCI₅ indicates the oxidation state of element Q in the compound, which is 5. From this information, we can determine the group number of element Q in the periodic table. Group number of an element is equal to its highest oxidation state. Since the oxidation state of element Q in the compound is 5, it belongs to group V of the periodic table. Therefore, the correct answer is V.

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Periodic Chemistry (Nigeria Only)

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Question 50 Report

Which of the following statement is correct? The solubility of

gases increases with increase in temperature

gases decreases with increase in temperature Correct answer

most solid solutes decreases with indease in temperature

most solid solutes is constant

Answer Details

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Question 51 Report

What is the value of -14^oC on the Kelvin temperature scale?

259K Correct answer

287 K

287^oK

259^oK

Answer Details

The Kelvin temperature scale is an absolute temperature scale where 0 Kelvin represents the lowest possible temperature (absolute zero). The Kelvin temperature scale is related to the Celsius scale by adding 273.15 to the Celsius value. To convert -14°C to Kelvin, we need to add 273.15 to the value. Thus, -14°C + 273.15 = 259.15 K. Therefore, the value of -14°C on the Kelvin temperature scale is 259 K (option a).

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