Q. No.The enthalpy of sublimation of a substance is equal to:
1. Enthalpy of fusion + Enthalpy of vaporization
2. Enthalpy of fusion
3. Enthalpy of vaporization
4. Twice the enthalpy of vaporization
(298K) of methanol is given by the chemical equation:
1. \(\mathrm{C}(\text { diamond })+\frac{1}{2} \mathrm{O}_{2(\mathrm{~g})}+2 \mathrm{H}_{2(\mathrm{~g})} \rightarrow \mathrm{CH}_3 \mathrm{OH}_{(\mathrm{l})}\)
2. \(\mathrm{CH}_{4(\mathrm{~g})}+\frac{1}{2} \mathrm{O}_{2(\mathrm{~g})} \rightarrow \mathrm{CH}_3 \mathrm{OH}_{(\mathrm{g})}\)
3. \(\mathrm{CO}_{(\mathrm{g})}+2 \mathrm{H}_{2(\mathrm{~g})} \rightarrow \mathrm{CH}_3 \mathrm{OH}_{(\mathrm{l})}\)
4. \(\mathrm{C}(\text { graphite })+\frac{1}{2} \mathrm{O}_{2(\mathrm{~g})}+2 \mathrm{H}_{2(\mathrm{~g})} \rightarrow \mathrm{CH}_3 \mathrm{OH}_{(\mathrm{l})}\)
The enthalpies of elements in their standard states are taken as zero. The enthalpy of formation of a compound is-
| 1. | Generally negative | 2. | Always positive |
| 3. | Zero | 4. | Never negative |
Determine the enthalpy of formation for , using the following enthalpies of reaction :
kJ/mol
kJ/mol
| 1. | -383 kJ/mol | 2. | -187 kJ/mol |
| 3. | -49 kJ/mol | 4. | None of the above |
\(\mathrm{2H_2(g) + O_2(g) \rightarrow 2H_2O(g); ~\Delta_rH^\circ = -483.64~ kJ }\)
What is the enthalpy change (in KJ) for the decomposition of one mole of water?
| 1. | 120.9 | 2. | 241.82 |
| 3. | 18 | 4. | 100 |
[Given : standard heat of formation of \(SO^{2-}_4\) ion (aq) \(= -216~ \text{kcal/mol}\), standard heat of crystallisation of \(BaSO_4 (s)= -4.5~\text{ kcal/mol,}\) standard heat of formation of \(BaSO_4 (s)= -349 ~\text{kcal/mol]}\)
1. \(+133.0 \)
2. \(+220.5\)
3. \(-128.5 \)
4. \(-133.0\)
When 4 g of iron is burnt to ferric oxide at a constant pressure, 29.28 kJ of heat is evolved.
The enthalpy of formation of ferric oxide will be-
(At. mass of Fe = 56) ?
1. 81.98 kJ
2. 819.8 kJ
3. 40.99 kJ
4. +819.8 kJ
Consider the following reaction,
S + O2 SO2, H = – 298.2 kJ mole–1
SO2 + 1/2 O2 SO3, H = – 98.7kJ mole–1
SO3 + H2O H2SO4 , H = – 130.2 kJ mole–1
H2 + 1/2 O2 H2O, H = – 287.3 kJ mole–1
the enthalpy of formation of H2SO4 at 298 K will be–
| 1. | – 814.4 kJ mole–1 | 2. | + 814.4 kJ mole–1 |
| 3. | – 650.3 kJ mole–1 | 4. | – 433.7 kJ mole–1 |
Which of the following is not an endothermic reaction?
1. Combustion of methane
2. Decomposition of water
3. Dehydrogenation of ethane or ethylene
4. Conversion of graphite to diamond
| Assertion (A): | Combustion of all organic compounds is an exothermic reaction. |
| Reason (R): | The enthalpies of all elements in their standard state are zero. |
| 1. | Both (A) and (R) are True and (R) is the correct explanation of (A). |
| 2. | Both (A) and (R) are True but (R) is not the correct explanation of (A). |
| 3. | (A) is True but (R) is False. |
| 4. | (A) is False but (R) is True. |
© 2025 GoodEd Technologies Pvt. Ltd.