Year : 
1991
Title : 
Chemistry
Exam : 
JAMB Exam

Paper 1 | Objectives

21 - 30 of 49 Questions

# Question Ans
21.

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)

A. 2.240 cm 3

B. 22.40 cm 3

C. 224.0 cm 3

D. 2240 cm 3

Detailed Solution

Na2CO3 + 2HCC → 2NaII + H2O
1000 cm3 IM Na2CO3 contains 22400 cm3
10cm3 IM Na2CO3 will contain (10) / (100) x 224
=224 cm3
10 cm3 0.1 Na2CO3 will contain (o.1 x 224) / (1) = 22.4 cm3
22.

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)

A. 1

B. 2

C. 3

D. 4

Detailed Solution

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
23.

Which of the following equimolar solutions, Na2CO3 Na2 SO
4CI FeCI3 CH3COONa,
have pH greater than 7?

A. FeCI 3 and NH 4CI

B. Na2CO3, CH3COONa and Na,Na2SO4

C. Na2CO3 and CH3COONa

D. FeCI3, CH3COONa and NH4CI

C
24.

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

A. 2

B. 3

C. 4

D. 5

Detailed Solution

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.
25.

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

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

B. a redox reaction in which SO2 is the oxidant and H2S is the reductant

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

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

Detailed Solution

In the above reaction, H\(_2\)S is oxidized to H\(_2\)O while SO\(_2\) is reduced to S. Hence, H\(_2\)S is the reductant while SO\(_2\) is the oxidant.
26.

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

A. increase the surface area of the reactants

B. increase the concntration of the reactants

C. lower the activation energy for the reaction

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

Detailed Solution

As a catalyst, MnO2 lowers activation energy of a reaction.
27.

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

A. -71.1

B. -4.18

C. +71.1

D. +111.0

Detailed Solution

Q = mct = (50 x 4.18 x 3.4) / (1000)
= 0.71606 kj
1.1 g of call2 contains
(1.1) / (111) = 0.01 moles of call2
If 0.01 liberates 0.7106 RS
1 will liberate (0.7106 x 1) / (0.01)
Exothermic = 71.06 = -71.1
28.

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?

A. Low temperature and high pressure

B. High temperature and low pressure

C. High temperature and high pressure

D. Low temperature and low pressure

A
29.

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

A. 2NaCI(s) ↔ 2Na (I) + CI2(g)

B. H 2(g) + I2(g) ↔ 2HI(g)

C. 2O3(g) ↔ 3O2(g)

D. 2NO2(g) ↔ N2O4(g)

Detailed Solution

The equilibrium concentrations of the products and reactants do not directly depend on the total pressure of the system. They may depend on the partial pressures of the products and reactants, but if the number of moles of gaseous reactants is equal to the number of moles of gaseous products, pressure has no effect on equilibrium.
30.

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

A. NO2

B. NO

C. N2O

D. CI2

C
21.

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)

A. 2.240 cm 3

B. 22.40 cm 3

C. 224.0 cm 3

D. 2240 cm 3

Detailed Solution

Na2CO3 + 2HCC → 2NaII + H2O
1000 cm3 IM Na2CO3 contains 22400 cm3
10cm3 IM Na2CO3 will contain (10) / (100) x 224
=224 cm3
10 cm3 0.1 Na2CO3 will contain (o.1 x 224) / (1) = 22.4 cm3
22.

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)

A. 1

B. 2

C. 3

D. 4

Detailed Solution

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
23.

Which of the following equimolar solutions, Na2CO3 Na2 SO
4CI FeCI3 CH3COONa,
have pH greater than 7?

A. FeCI 3 and NH 4CI

B. Na2CO3, CH3COONa and Na,Na2SO4

C. Na2CO3 and CH3COONa

D. FeCI3, CH3COONa and NH4CI

C
24.

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

A. 2

B. 3

C. 4

D. 5

Detailed Solution

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.
25.

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

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

B. a redox reaction in which SO2 is the oxidant and H2S is the reductant

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

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

Detailed Solution

In the above reaction, H\(_2\)S is oxidized to H\(_2\)O while SO\(_2\) is reduced to S. Hence, H\(_2\)S is the reductant while SO\(_2\) is the oxidant.
26.

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

A. increase the surface area of the reactants

B. increase the concntration of the reactants

C. lower the activation energy for the reaction

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

Detailed Solution

As a catalyst, MnO2 lowers activation energy of a reaction.
27.

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

A. -71.1

B. -4.18

C. +71.1

D. +111.0

Detailed Solution

Q = mct = (50 x 4.18 x 3.4) / (1000)
= 0.71606 kj
1.1 g of call2 contains
(1.1) / (111) = 0.01 moles of call2
If 0.01 liberates 0.7106 RS
1 will liberate (0.7106 x 1) / (0.01)
Exothermic = 71.06 = -71.1
28.

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?

A. Low temperature and high pressure

B. High temperature and low pressure

C. High temperature and high pressure

D. Low temperature and low pressure

A
29.

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

A. 2NaCI(s) ↔ 2Na (I) + CI2(g)

B. H 2(g) + I2(g) ↔ 2HI(g)

C. 2O3(g) ↔ 3O2(g)

D. 2NO2(g) ↔ N2O4(g)

Detailed Solution

The equilibrium concentrations of the products and reactants do not directly depend on the total pressure of the system. They may depend on the partial pressures of the products and reactants, but if the number of moles of gaseous reactants is equal to the number of moles of gaseous products, pressure has no effect on equilibrium.
30.

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

A. NO2

B. NO

C. N2O

D. CI2

C