Q. No.Consider the given reaction"
\(2 Zn(s) + O_2 (g) \rightarrow 2ZnO(s)\)
For this reaction, \(\Delta H = -693.8~ \text {kJ mol}^{-1}\).
The correct statements among the following are :
| a. | The enthalpy of two moles of ZnO is less than the total enthalpy of two moles of Zn and one mole of oxygen by 693.8 kJ. |
| b. | The enthalpy of two moles of ZnO is more than the total enthalpy of two moles of Zn and one mole of oxygen by 693.8 kJ. |
| c. | 693 . 8 kJ mol -1 energy is evolved in the reaction. |
| d. | 693 . 8 kJ mol -1 energy is absorbed in the reaction. |
1. a and b
2. b and c
3. c and d
4. a and c
A sample containing 1.0 mol of an ideal gas undergoes an isothermal, reversible expansion to ten times its original volume in two separate experiments. The expansion is carried out at temperatures of 300 K and 600 K, respectively.
The correct statements among the following are:
| (a) | Work done at 600 K is 20 times the work done at 300 K. |
| (b) | Work done at 300 K is twice the work done at 600 K. |
| (c) | Work done at 600 K is twice the work done at 300 K. |
| (d) | ∆ U = 0 in both cases. |
1. (a) and (b)
2. (b) and (c)
3. (c) and (d)
4. (a) and (d)
The processes among the following that occur spontaneously are :
| (a) | The flow of heat from a colder to a warmer body. |
| (b) | Gas in a container contracting into one corner. |
| (c) | Gas expanding to fill the available volume. |
| (d) | Burning carbon in oxygen to give carbon dioxide. |
1. (a, b)
2. (b, c)
3. (c, d)
4. (a, d)
In an exothermic reaction, heat is evolved, and the system loses heat to the surrounding. The correct choice among the following for such a system are-
(a) qp will be negative
(b) will be negative
(c) qp will be positive
(d) will be positive
1. (a, b)
2. (b, c)
3. (c, d)
4. (a, d)
Thermodynamics primarily focuses on:
| (a) | Interrelation of various forms of energy and their transformation from one form to another. |
| (b) | Energy changes in the processes depend only on the initial and final states of the microscopic systems containing a few molecules. |
| (c) |
The mechanisms and rates at which energy transformations occur. |
| (d) |
Whether a system is in an equilibrium state or transitioning between one equilibrium state and another. |
The correct statements, among the above, are:
1. (a) and (b)
2. (b) and (c)
3. (c) and (d)
4. (a) and (d)
| Assertion (A): | A liquid crystallizes into a solid and is accompanied by a decrease in entropy. |
| Reason (R): | In crystals, molecules organize in an ordered manner. |
| 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. |
| Assertion (A): | Spontaneous process is an irreversible process and may be reversed by some external agency. |
| Reason (R): | A decrease in enthalpy is a contributing factor to spontaneity. |
| 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. |
| 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. |
Match the statements given in column 1 with corresponding characteristics given in column II and choose the correct option:
| Column -I | Column -II | ||
| A. | Entropy of vaporization | 1. | Decreases |
| B. | K for a spontaneous process | 2. | Is always positive |
| C. | Crystalline solid state | 3. | Lowest entropy |
| D. | \(\Delta U\) in an adiabatic expansion of ideal gas | 4. | \(\Delta H_{vap} \over T_b\) |
Codes:
| Options: | A | B | C | D |
| 1. | 2,4 | 2 | 3 | 1 |
| 2. | 1 | 2 | 3 | 4 |
| 3. | 1 | 4,3 | 3 | 2 |
| 4. | 4 | 3 | 3,1 | 2 |
Match the following parameters with a description for spontaneity.
| \(\Delta r\ H^⊝\) | \(\Delta r\ S^⊝\) | \(\Delta r\ G^⊝\) | Description | ||
| A. | + | – | + | 1. | Non-spontaneous at high temperature |
| B. | – | – | + | 2. | Spontaneous at all temperatures |
| C. | – | + | – | 3. | Non-spontaneous at all temperatures |
Codes:
| A | B | C | |
| 1. | 3 | 1 | 2 |
| 2. | 1 | 2 | 3 |
| 3. | 1 | 3 | 2 |
| 4. | 3 | 2 | 1 |
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