- 1(current)
Q. No.Select the correct option based on statements given below:
| 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. |
Subtopic: Thermochemistry |
79%
Level 2: 60%+
Hints
On the basis of thermochemical equations (i), (ii), and (iii), find out which of the algebraic relationships given in options (a) to (d) is correct:
| (i) | C(graphite) + O2(g) → CO2 (g) ; ∆rH = x kJmol-1 |
| (ii) | C(graphite) + \(\frac{1}{2}\)O2(g) → CO(g) ; ∆rH = y kJ mol-1 |
| (iii) | CO(g) + \(\frac{1}{2}\)O2(g) → CO2(g); ∆rH = z kJ mol-1 |
1. z=x+y
2. x=y-z
3. x=y+z
4. y=2z-x
Subtopic: Thermochemistry |
77%
Level 2: 60%+
Hints
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 |
Subtopic: Thermochemistry |
57%
Level 3: 35%-60%
Hints
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
Subtopic: Thermochemistry |
87%
Level 1: 80%+
Hints
- 1(current)
Q. No.
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