JAMB UTME - Chemistry - 2019

Tazama Jibu

Swali 2 Ripoti

2-methylprop-1-ene is an isomer of

3-methyl but-1-ene

2-methyl but-1-ene

but-2-ene

pent-2-ene

Tazama Jibu

Swali 3 Ripoti

What mass of magnesium would be obtained by passing a current of 2 amperes for 2 hours, through molten magnesium chloride?
[1 faraday = 96500C, Mg = 24]

1.12g

4.48g

1.80g

2.00g

Maelezo ya Majibu

Current (I) = 2A; Time (t) = 2 hours = 7200 secs
Q = It
= 2 x 7200 = 14400C
1 F = 96500C
x = 14400C
x = $\frac{14400}{96500}$
= 0.15F
Mg $^{2 +}$ + 2e $^{-}$ $\to$ Mg
2F $\to$ 24g
0.15F $\to$ x
2x = 24 x 0.15
x = $\frac{24 \times 0.15}{2}$
= 1.8g

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

Read lesson note on Electrolysis (JAMB)

Chemical Kinetics And Equilibrium Systems (Ghana Only)

Electrolysis

Tazama Jibu

Swali 4 Ripoti

The part of the total energy of a system that accounts for the useful work done in a system is known as

Enthalpy change

None of the above

Gibb's free energy

Entropy

Energy Changes

Tazama Jibu

Swali 5 Ripoti

Which of the following gases contains the least number of atoms at s.t.p?

1 mole of butane

4 moles of chlorine

3 moles of ozone

7 moles of argon

Tazama Jibu

Swali 6 Ripoti

The two ions responsible for hardness in water are

Ca

^{2 +}

and / or Mg

^{2 +}

K

^{+}

and / or Mg

^{2 +}

Ca

^{2 +}

and / or Li

^{+}

Ca

^{2 +}

and / or Na

^{+}

Solubility

Water

Tazama Jibu

Swali 7 Ripoti

The shapes of water, ammonia, carbon (iv) oxide and methane are respectively

linear, tetrahedral, angular and pyramidal

angular, pyramidal, linear and tetrahedral

pyramidal, linear, tetrahedral and angular

tetrahedral, angular, pyramidal and linear

Tazama Jibu

Swali 8 Ripoti

What volume of 0.100M sodium trioxonitrate (V) solution contains 5g of solute.

[Na = 23, N = 14, O = 16]

1.7 litres

0.420 litres

0.588 litres

2.35 litres

Stoichiometry And Chemical Reactions

Tazama Jibu

Swali 9 Ripoti

The electronic configuration of element Z is 1s $^{2}$ 2s $^{2}$ 2p $^{6}$ 3s $^{2}$ 3p $^{1}$ . What is the formula of the compound formed between Z and tetraoxosulphate (VI) ion.

Z

_{3}

(SO

_{4}

)

_{2}

ZSO

_{4}

Z

_{2}

SO

_{4}

Z

_{2}

(SO

_{4}

)

_{3}

Maelezo ya Majibu

Z = 1s $^{2}$ 2s $^{2}$ 2p $^{6}$ 3s $^{2}$ 3p $^{1}$
$∴$ We have Z $^{3 +}$ and SO $_{4}^{2 -}$
The reaction : Z $^{3 +}$ + SO $_{4}^{2 -}$ $\to$ Z $_{2}$ (SO $_{4}$ ) $_{3}$ .

Read lesson note on Atomic Structure And Bonding (JAMB)

Tazama Jibu

Swali 10 Ripoti

200cm $^{3}$ of 0.50mol/dm $^{3}$ solution of calcium hydrogen trioxocarbonate (IV) is heated. The maximum weight of solid precipitated is

10g

25g

20g

15g

Maelezo ya Majibu

To solve this problem, we need to use the concept of stoichiometry and the solubility product constant (Ksp) of calcium hydrogen trioxocarbonate (IV). First, we need to write the balanced equation for the reaction that occurs when the solution of calcium hydrogen trioxocarbonate (IV) is heated: Ca(HCO3)2(s) → CaCO3(s) + H2O(g) + CO2(g) From the balanced equation, we can see that 1 mole of calcium hydrogen trioxocarbonate (IV) produces 1 mole of calcium carbonate. Therefore, we need to determine the number of moles of calcium hydrogen trioxocarbonate (IV) in the solution: Number of moles = concentration x volume Number of moles = 0.50 mol/dm³ x 0.2 dm³ Number of moles = 0.1 mol Since 1 mole of calcium hydrogen trioxocarbonate (IV) produces 1 mole of calcium carbonate, the number of moles of calcium carbonate produced will also be 0.1 mol. Next, we need to use the solubility product constant (Ksp) of calcium carbonate to determine the maximum amount of solid that can be precipitated: Ksp = [Ca²⁺][CO3²⁻] Ksp = 3.3 x 10⁻⁹ (at 25°C) At the maximum amount of solid precipitated, all the calcium carbonate formed will have precipitated, and the concentration of calcium ions and carbonate ions will be equal. Therefore, we can assume that the concentration of calcium ions and carbonate ions is both x. Substituting into the Ksp expression: Ksp = x² 3.3 x 10⁻⁹ = x² x = 5.74 x 10⁻⁵ mol/dm³ The mass of calcium carbonate precipitated can now be calculated: Mass = number of moles x molar mass Mass = 0.1 mol x 100.1 g/mol Mass = 10.01 g Therefore, the maximum weight of solid precipitated is approximately 10 g. Note that this calculation assumes that all the calcium carbonate precipitated as a solid, which may not always be the case in a real-world experiment. Additionally, this calculation does not take into account any losses due to filtration or other experimental errors.

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

Tazama Jibu

Swali 11 Ripoti

Which of the following pairs cannot be represented with a chemical formula?

air and bronze

bronze and sodium chloride

copper and sodium chloride

caustic soda and washing soda

Metals And Their Compounds

Tazama Jibu

Swali 12 Ripoti

A secondary alkanol can be oxidized to give an

alkanone

alkyne

alkanoic acid

alkanal

Tazama Jibu

Swali 13 Ripoti

When the end alkyl groups of ethyl ethanoate are interchanged, the compound formed is

propylmethanoate

ethylpropanoate

methyl ethanoate

methyl propanoate

Tazama Jibu

Swali 14 Ripoti

Which of the following reactions is an oxidation process?

2H

^{+}

+ 2e

^{-}

\to

H

_{2}

2O

^{2 -}

+ 4e

^{-}

\to

O

_{2}

OCl

^{-}

+ H

_{2}

O + 2e

^{-}

\to

2OH

^{-}

+ Cl

^{-}

Cl + e

^{-}

\to

Cl

^{-}

Oxidation And Reduction

Tazama Jibu

Swali 15 Ripoti

If the cost of electricity required to discharge 10g of an ion X $^{3 +}$ is N20.00, how much would it cost to discharge 6g of ion Y $^{2 +}$ ?

[1 faraday = 96,500C, atomic masses are X = 27, Y = 24]

N10.00

N6.00

N20.00

N9.00

Maelezo ya Majibu

X $^{3 +}$ + 3e $^{-}$ $\to$ X
3F = 27g
xF = 10g
$\frac{x}{3} = \frac{10}{27} ⟹ x = \frac{10}{9} F$
$\frac{10}{9}$ F $\equiv$ N20.00
1F is equivalent to x
$\frac{1}{\frac{10}{9}} = \frac{x}{20}$
$\frac{9}{10} = \frac{x}{20} ⟹ x = N 18.00$
1F is equivalent to N18.00.
Y $^{2 +}$ + 2e $^{-}$ $\to$ Y
2F = 24g
xF = 6g
x = $\frac{6 \times 2}{24} = \frac{1}{2} F$
1F = N18.00
$\frac{1}{2}$ F = $\frac{1}{2} \times N 18.00$
= N9.00

Tazama Jibu

Swali 16 Ripoti

In the reaction between sodium hydroxide and tetraoxosulphate (VI) solutions, what volume of 0.5 molar sodium hydroxide would exactly neutralize 10cm $^{3}$ of 1.25 molar tetraoxosulphate (vi) acid?

25cm

^{3}

10cm

^{3}

20cm

^{3}

50cm

^{3}

Maelezo ya Majibu

Equation of reaction : 2NaOH + H $_{2}$ SO $_{4}$ → Na $_{2}$ SO $_{4}$ + 2H $_{2}$ O

Concentration of a base, CB = 0.5M

Volume of acid, V $_{A}$ = 10cm $^{3}$

Concentration of an acid, C $_{A}$ = 1.25M

Volume of base, V $_{B}$ = ?

Recall:
$\frac{C_{A} V_{A}}{C_{B} V_{B}} = \frac{n_{A}}{n_{B}}$ ... (1)
N.B: From the equation,
$\frac{n_{A}}{n_{B}} = \frac{1}{2}$

From (1)
$\frac{1.25 \times 10}{0.5 \times V_{B}} = \frac{1}{2}$
$\frac{12.5}{0.5 V_{B}} = \frac{1}{2}$
25 = 0.5V $_{B}$

VB = 50.0 cm $^{3}$

Read lesson note on Stoichiometry And Chemical Reactions (WAEC)

Stoichiometry And Chemical Reactions

Tazama Jibu

Swali 17 Ripoti

What technique is suitable for separating a binary solution of potassium chloride and potassium trioxochlorate (V)?

Fractional crystallization

Fractional distillation

Filtration

Evaporation

Separation Of Mixtures And Purification Of Chemical Substances

Tazama Jibu

Swali 18 Ripoti

Hydrocarbons which will react with Tollen's reagent conform to the general formula

C

_{n}

H

_{2 n}

C

_{n}

H

_{2 n + 2}

C

_{n}

H

_{2 n - 2}

C

_{n}

H

_{2 n + 1}

OH

Tazama Jibu

Swali 19 Ripoti

When ammonia and hydrogen ion bond together to form ammonium ion, the bond formed is called

electrovalent bond

co-ordinate bond

ionic bond

covalent bond

Oxidation And Reduction

Tazama Jibu

Swali 20 Ripoti

Which of the following does not support the fact that air is a mixture?

the constituents of air are in a fixed proportion by mass

it cannot be represented with a chemical formula

the constituents of air can be separated by physical by physical means

none of the above

Air

Tazama Jibu

Swali 21 Ripoti

Hydrogen diffused through a porous plug

thrice as fast as oxygen

at the same speed as oxygen

four times as fast as oxygen

twice as fast as oxygen

Acids, Bases And Salts (Nigeria Only)

Tazama Jibu

Swali 22 Ripoti

The cost of discharging 6.0g of a divalent metal, X from its salt is ₦12.00. What is the cost of discharging 9.0g of a trivalent metal, Y from its salt under the same condition?

[X = 63, Y = 27, 1F = 96,500C]

N12.00

N27.00

N63.00

N95.00

Maelezo ya Majibu

For X: X $^{2 +}$ + 2e $^{-}$ $\to$ X
2F = 63g
xF = 6g
x = $\frac{6 \times 2}{63} = \frac{4}{21} F$
$\frac{4}{21}$ F = N12.00
1F = $\frac{12}{\frac{4}{21}}$
= N63.00
1F is equivalent to N63.00.
For Y: Y $^{3 +}$ + 3e $^{-}$ $\to$ Y
3F = 27g
xF = 9g
x = $\frac{3 \times 9}{27}$
= 1F
1F = N63.00

Read lesson note on Chemical Combination (JAMB)

Chemical Combination

Tazama Jibu

Swali 23 Ripoti

Sulphur exists in six forms in the solid state. This property is known as

Isomerism

Allotropy

Isotopy

Isomorphism

Non-metals And Their Compounds

Tazama Jibu

Swali 24 Ripoti

When chlorine water is exposed to bright sunlight, the following products are formed

HCl

_{(a q)}

and Cl

_{2}

HOCl

_{(a q)}

and Cl

_{2}

HCl

_{(a q)}

and O

_{2}

HOCl

_{(a q)}

and O

_{2}

Chemistry Of Carbon Compounds (Ghana Only)

Tazama Jibu

Swali 25 Ripoti

Methane is prepared in the laboratory by heating a mixture of sodium ethanoate with soda lime. The chemical constituent(s) of soda lime is/are

Ca(OH)

_{2}

and NaOH

Na

_{2}

CO

_{3}

NaCl

NaOH

Chemical Combination

Tazama Jibu

Swali 26 Ripoti

Which process(es) is/are involved in the turning of starch iodide paper blue-black by chlorine gas?

chlorine attacks the starch to give the blue-black color

chlorine attacks the iodide ion to give the blue-black color

chlorine oxidizes the iodide ion to produce iodine which attacks the starch to give the blue-black color

iodine attacks the starch to give the blue-black color

Energy And Energy Changes

Tazama Jibu

Swali 27 Ripoti

X is a substance which liberates CO $_{2}$ on treatment with concentrated H $_{2}$ SO $_{4}$ . A warm solution of X can decolorize acidified KMnO $_{4}$ . X is

HCOOH

NaHCO

_{3}

FeCO

_{3}

H

_{2}

C

_{2}

O

_{4}

Maelezo ya Majibu

It should be noted that for X to liberate CO $_{2}$ , X must be a carbonate or an oxalate. Since X decolorizes KMnO $_{4}$ , X must be an oxalate.
Therefore, X is H $_{2}$ C $_{2}$ O $_{4}$ .

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

Periodic Chemistry (Ghana Only)

Tazama Jibu

Swali 28 Ripoti

Which two gases can be used for the demonstration of the fountain experiment?

SO

_{3}

and NH

_{3}

SO

_{2}

and NH

_{3}

HCl and NH

_{3}

SO

_{2}

and HCl

Tazama Jibu

Swali 29 Ripoti

A cell shorthand notation can be written as A / A $^{+}$ // B $^{2 +}$ /B. The double slash in the notation represents the

electrolyte

electrodes

salt bridge

solid - liquid interface

Electrolysis

Tazama Jibu

Swali 30 Ripoti

Which of the following describes the chemical property of acids?

None of the above

Acid + XCO

_{3}

\to

Salt + H

_{2}

O + NH

_{3}

Acid + NaOH

\to

Normal salt + CO

_{2}

Acid + X

_{n}

CO

_{3}

\to

Salt + H

_{2}

O + CO

_{2}

Acids, Bases And Salts

Tazama Jibu

Swali 31 Ripoti

Consider the reaction

A $_{(s)}$ + 2B $_{(g)}$ → 2C $_{(a q)}$ + D $_{(g)}$

What will be the effect of a decrease in pressure on the reaction?

the equilibrium will shift

rate of forward reaction will increase

rate of backward reaction will increase

rates of forward and backward reaction are not affected

Maelezo ya Majibu

Given: The equation below

A $_{(s)}$ + 2B $_{(g)}$ → 2C $_{(a q)}$ + D $_{(g)}$

Since we have a higher number of moles of gaseous species on the LHS, i.e 2, a decrease in pressure will favor the forward reaction.

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

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

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

Chemical Kinetics And Equilibrium Systems (Ghana Only)

Periodic Chemistry (Ghana Only)

Tazama Jibu

Swali 32 Ripoti

Which of the following factors will speed up the rate of evolution of carbon (iv) oxide in the reaction below?

2HCl + CaCO $_{3}$ → CaCl $_{2}$ + H $_{2}$ O + CO $_{2}$

Increasing the concentration of the acid

Increasing the surface area of CaCO

_{3}

A and B

Reducing the concentration of the acid

Oxidation And Reduction

Tazama Jibu

Swali 33 Ripoti

A solution X, on mixing with AgNO $_{3}$ solution gives a white precipitate soluble in aqueous NH $_{3}$ , a solution Y, when also added to X, also gives a white precipitate which is soluble when heated solutions X and Y respectively contain

Al

^{3 +}

, Cl

^{-}

Hg

^{+}

, SO

_{4}^{2 -}

Pb

^{2 +}

, Cl

^{-}

Ag

^{+}

, SO

_{4}^{2 -}

Chemistry Of Carbon Compounds (Ghana Only)

Tazama Jibu

Swali 34 Ripoti

If acidified Potassium Dichromate(VI) (K $_{2}$ Cr $_{2}$ O $_{7}$ ) acts as oxidizing agent, color changes from

yellow to green

orange to green

yellow to red

orange to red

Oxidation And Reduction

Tazama Jibu

Swali 35 Ripoti

How many alkoxyalkanes can be obtained from the molecular formula C $_{4}$ H $_{10}$ O?

4

2

1

3

Acids, Bases And Salts (Nigeria Only)

Chemical Equilibra

Tazama Jibu

Swali 36 Ripoti

By what amount must the temperature of 200cm $^{3}$ of Nitrogen at 27°C be increased to double the pressure if the final volume is 150cm $^{3}$ (Assume ideality)

150°C

177°C

75°C

120°C

Maelezo ya Majibu

Using the ideal gas law and equation:
$\frac{P_{1} V_{1}}{T_{1}} = \frac{P_{2} V_{2}}{T_{2}}$
$\frac{P_{1} \times 200 {cm}^{3}}{300 K} = \frac{2 P \times 150 {cm}^{3}}{T_{2}}$
Cross multiply:
$T_{2} = \frac{300 \times 150 \times 2 P}{200 \times P}$
$= 450 K$ or $177^{\circ} C$
Don't forget to convert to $^{\circ} C$

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