If enthalpies of formation of C₂H₄(g), CO₂(g) and H₂O(l) at 25°C and 1 atm pressure be 52, – 394 and –286 kJ mol^–1 respectively, the enthalpy of combustion of C₂H₄(g) will be [CBSE PMT 1995; AIIMS 1998; Pb. PMT 1999]

(1) +1412 kJ mol^–1

(2) –1412 kJ mol^–1

(3) +141.2 kJ mol^–1

(4) –141.2 kJ mol^–1

Ozone is prepared by passing silent electric discharge through oxygen. In this reaction [AFMC 1998]

(1) Energy is given out

(2) Energy is absorbed

(3) Oxygen is loaded with energy

(4) Oxygen is dissociated into atoms

Combustion of glucose takes place according to the equation,

${\mathrm{C}}_6{\mathrm{H}}_{12}{\mathrm{O}}_6+6{\mathrm{O}}_2\to 6{\mathrm{CO}}_2+6{\mathrm{H}}_2\mathrm{O}$, $∆ H = -72 K cal$

Energy required for the production of 1.6 g of glucose is -

(Molecular mass of glucose = 180 g)

1. 0.064 kcal

2. 0.64 kcal

3. 6.4 kcal

4. 64 kcal

Which of the following compounds will absorb the maximum quantity of heat when dissolved in the same amount of water ? The heats of solution of these compounds at 25°C in kJ/mole of each solute is given in brackets [AMU (Engg.) 2000]

(1) $HN{O}_3(\Delta H=-33)$

(2) $KCl(\Delta H=+17.64)$

(3) $N{H}_{4}N{O}_3(\Delta H=+25.5)$

(4) $HCl(\Delta H=-74.1)$

A system is changed from state A to state B by one path and from B to A by another path. If E₁ and E₂ are the corresponding changes in internal energy, then [Pb. PMT 2001]

1. $E_1+E_2=-ve$

2. $E_1+E_2=+ve$

3. $E_1+E_2=0$

4. None of the above

If (i) $C+O_2\to C{O}_2$, (ii) $C+1/2O_2\to CO$, (iii) $CO+1/2O_2\to C{O}_2$, the heats of reaction are Q, –12, –10 respectively. Then Q = [Orissa JEE 2004]

(1) – 2

(2) 2

(3) – 22

(4) – 16

Adsorption of gases on a solid surface is generally exothermic because [IIT JEE (Screening) 2004]

1. Enthalpy is positive

2. Entropy decreases

3. Entropy increases

4. Free energy increase

Two mole of an ideal gas is expanded isothermally and reversibly from 1 litre ot 10 litre at 300 K. The enthalpy change (in kJ) for the process is [IIT JEE (Screening) 2004]

1. 11.4 kJ

2. –11.4 kJ

3. 0 kJ

4. 4.8 kJ

When a gas undergoes adiabatic expansion, it gets cooled due to -

1. Loss of energy

2. Fall in pressure

3. Decrease in velocity

4. Increase in energy with work done

In an isobaric process, the ratio of heat supplied to the system (dQ) and work done by the system (dW) for diatomic gas is [AFMC 2002]

(1) 1 : 1

(2) 7 : 2

(3) 7 : 5

(4) 5 : 7