JAMB Chemistry Past Questions & Answers - Page 296

1,476.

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

A.

NO2

B.

NO

C.

N2O

D.

CI2

Correct answer is C

No explanation has been provided for this answer.

1,477.

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)

Correct answer is B

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.

1,478.

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

Correct answer is A

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

are; i low temperature since the forward reaction is endothermic and backward reaction is exothermic.

       ii high pressure since forward reaction involves a reduction in volume and backward reaction involves an increase in volume. ( reaction is in the gaseous phase).

1,479.

1.1 g of CaCI2 dissolved in 50 cm3 of water caused a rise in temperature of 3.4°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

Correct answer is A

Q = mct = (50 x 4.18 x 3.4) / (1000)
= 0.71606 kj
1.1 g of \(CaCl_2\) contains
(1.1) / (111) = 0.01 moles of \(CaCl_2\)
If 0.01 liberates 0.7106 quantity of heat.
1 will liberate (0.7106 x 1) / (0.01)
Exothermic = 71.06 = -71.1

1,480.

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 reactio

D.

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

Correct answer is C

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