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

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