Thermodynamics Test

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Thermodynamics Test - 76

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Weekly Quiz Competition

Question 1
1 / -0

For the reaction :

$$3N_{2} + H_{2} \rightarrow 2NH_{3}$$,

$$\triangle H = - 24 kcal$$ at $$427^{0}C$$ and $$200 atm$$

Calculate magnitude of internal enerrgy change in $$Kcal$$ ($$\triangle U$$), if 168 g $$N_{2}$$ gas and 30 g $$H_{2}$$ gas are allowed to react completely (100% reaction yield) to form $$NH_{3}$$ gas at $$427^{0}C$$ and 200 atm.

A
- 106 kcal

B
- 24 kcal

C
- 21.2 kcal

D
- 120 kcal
Question 2
1 / -0

Which of the following are spontaneous?

A
dissolution of sugar

B
separation of Ar and Kr from their mixture

C
spreading of fragrance when a bottle of perfume is opened

D
Flow of heat from cold object to hot object

E
heat transfer from ice to room at $$ 25^0 C $$
Question 3
1 / -0

One mole of an ideal monatomic gas undergoes a process described by the equation $$PV^{3}$$ = constant. The heat capacity of the gas during this process is:

A
$$R$$

B
$$\dfrac{3}{2R}$$

C
$$\dfrac{5}{2R}$$

D
$${2R}$$
Question 4
1 / -0

A reaction A(g) +B(g) $$\rightarrow $$ C(g) +D(g). $$\Delta H$$= (-) ve is found to have positive entropy change. the reaction will be:

A
Spontaneous at high temperature

B
Spontaneous only at low temperature

C
Not spontaneous at any temperature

D
Spontaneous at any temperature

Solution
Question 5
1 / -0

The correct thermodynamic conditions for the spontaneous reaction at all temperatures is ______________________.

A
$$\Delta H < 0 \quad and\quad \Delta S < 0$$

B
$$\Delta H < 0 \quad and\quad \Delta S = 0$$

C
$$\Delta H > 0 \quad and\quad \Delta S < 0$$

D
$$\Delta H < 0 \quad and\quad \Delta S > 0$$

Solution
Question 6
1 / -0

7.5 KJ heat is added to a closed system and its internal energy decreases by 12 KJ. So,______ of work is done ____ the system ,for a new process , if the work is zero, then____of heat is ______ for the same changes in state of system

A
4.5 KJ on, 12 KJ released

B
19.5 KJ by, 12 KJ released

C
4.5 KJ by, 12 KJ released

D
19.5 KJ on, 12 KJ released
Question 7
1 / -0

An ideal monoatomic gas is taken through a process in which $$d Q = 2 d U$$ . The molar heat capacity of the gas for the process is

A
$$R$$

B
$$2R$$

C
$$3R$$

D
$$4R$$

Solution
Question 8
1 / -0

Correct desending order of deprotonation in the following compound:

A
e > d > c > b > a

B
e > d > c > a > b

C
e > c > b > d > a

D
e > c > b > a > d
Question 9
1 / -0

$$100g$$ of water is heated from $${30}^{o}C$$ to $${50}^{o}C$$. Ignoring the slight expansion of water, the change in its internal energy is (Specific heat of water is $$4200J$$ $${kg}^{-1}$$ $${K}^{-1}$$)

A
$$4.2kJ$$

B
$$84kJ$$

C
$$2.1kJ$$

D
$$8.4kJ$$

Solution
Question 10
1 / -0

If $$\Delta G_{298}$$ for reaction:
$$2H_{2 (9, 1 atm)} + O_{2(g)(1atm)} \to 2H_2O(g)(1 atm)$$
is $$-240KJ$$, what will be the $$\Delta G_{298}$$ for reaction
$$H_2O_{(g, 0.2atm)} \to H_{2(g, 4atm)} + \dfrac{1}{2}O_{2(g, 0.9 atm)}$$

A
$$245.7 KJ$$

B
$$239.3 KJ$$

C
$$125.70KJ$$

D
$$-245.7 KJ$$

Solution

For one mole $$H_2O$$ formation at 1atm
$$= \dfrac{-240}{2} = -120 kJ$$
For decomposition $$=+120KJ$$
$$Kep = P \left[\dfrac{\sqrt{O_2} \times H_2}{420}\right] = \dfrac{\sqrt{0.25}\times 4}{0.2}$$
$$= 0.5\times 20$$
$$= 10$$

$$\Delta G = \Delta G^o + RT\ ln K$$
$$ = 120000+ 8.314\times 298 \times ln 10$$
$$= 125705 J$$
$$= 125.7 KJ$$