The enthalpy of combustion at 25°C of H₂, cyclohexane (C₆H₁₂) and cyclohexene (C₆H₁₀) are –241, –3920 and –3800 KJ / mole respectively. The heat of hydrogenation of cyclohexene is

(1) – 121 KJ / mole

(2) + 121 KJ / mole

(3) – 242 KJ / mole

(4) + 242 KJ / mole

The heat change for the reaction $H_{2 \left(g\right)} +\frac{1}{2}{O}_{2 \left(g\right)}\to H_{2}O$(l) is called

1. Heat of reaction

2. Heat of formation

3. Heat of vaporization

4. None of the above

The heat of neutralisation of a strong acid and a strong alkali is 57.0 kJ mol^–1. The heat released when 0.5 mole of HNO₃ solution is mixed with 0.2 mole of KOH is [KCET 1991; AIIMS 2002; 

(1) 57.0 kJ

(2) 11.4 kJ

(3) 28.5 kJ

(4) 34.9 kJ

A solution of 500 ml of 0.2 M KOH and 500 ml of 0.2 M HCl is mixed and stirred; the rise in temperature is T₁. The experiment is repeated using 250 ml each of solution, the temperature raised is T₂. Which of the following is true

(1) T₁ = T₂

(2) T₁ = 2T₂

(3) T₁ = 4T₂

(4) T₂ = 9T₁

In the reaction for the transition of carbon in the diamond form to carbon in the graphite form, ΔH is –453.5 cal. This points out that

(1) Graphite is chemically different from diamond

(2) Graphite is as stable as diamond

(3) Graphite is more stable than diamond

(4) Diamond is more stable than graphite

Which of the following equations correctly represents the standard heat of formation $\left(\Delta H_f^o\right)$ of methane [IIT JEE (Screening) 1992]

(1) $C\left(diamond\right)+2H_2\left(g\right)=C{H}_4\left(g\right)$

(2) $C\left(graphite\right)+2H_2\left(g\right)=C{H}_4\left(l\right)$

(3) $C\left(graphite\right)+2H_2\left(g\right)=C{H}_4\left(g\right)$

(4) $C\left(graphite\right)+4H=C{H}_4\left(g\right)$

In which of the following reactions does the heat change represent the heat of the formation of water

1. $2H_2\left(g\right)+O_2\left(g\right)\to 2H_{2}O\left(l\right);\Delta H=-116kcal$

2. $H_2\left(g\right)+\frac{1}{2}{O}_2\left(g\right)\to H_{2}O\left(l\right);\Delta H=-58kcal$

3. $H^{+}(aq.)+O{H}^{-}(aq.)\to 2H_{2}O\left(l\right);\Delta H=-13.7kcal$

4. $C_2{H}_2\left(g\right)+2\frac{1}{2}{O}_2\left(g\right)\to 2C{O}_2\left(g\right)+H_{2}O\left(l\right)$; $\Delta H=-310kcal$

Based on the following thermochemical equations

$H_{2}O\left(g\right)+C\left(s\right)\to CO\left(g\right)+H_2\left(g\right);\Delta H=131kJ$

$CO\left(g\right)+\frac{1}{2}{O}_2\left(g\right)\to C{O}_2\left(g\right);\Delta H=-282kJ$

$H_2\left(g\right)+\frac{1}{2}{O}_2\left(g\right)\to H_{2}O\left(g\right);\Delta H=-242kJ$

$C\left(s\right)+O_2\left(g\right)\to C{O}_2\left(g\right);\Delta H=XkJ$

The value of X is [CBSE PMT 1992]

(1) –393 kJ

(2) –655 kJ

(3) +393 kJ

(4) +655 kJ

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