1. ⇒ (MHT CET 2023 12th May Morning Shift )

Calculate amount of methane formed by liberation of $149.6 kJ$ of heat using following equation.

$C_{(s)} + 2 H_{2 (g)} ⟶ {CH}_{4 (g)} Δ H = - 74.8 kJ / mol$

A. 16 g

B. 24 g

C. 32 g

D. 48 g

Correct Option is (C)

According to the given reaction, $74.8 kJ$ of heat is evolved when $1 mol$ of methane is formed.

$\begin{aligned} 74.8 kJ \equiv 1 mol {CH}_{4} = 16 g {CH}_{4} \\ 149.6 kJ \equiv x g {CH}_{4} \\ x = \frac{149.6 \times 16}{74.8} = 32 g \end{aligned}$

2. ⇒ (MHT CET 2023 10th May Evening Shift )

If $8.84 kJ$ heat is liberated for formation of $3 g$ ethane, calculate its $△_{f} H^{\circ}$ .

A. $- 8.00 kJ$

B. $15.0 kJ$

C. $30.0 kJ$

D. $- 84.4 kJ$

Correct Option is (D)

Formation of ethane:

$2 C_{(s)} + 3 H_{2 (g)} ⟶ C_{2} H_{6 (g)}; Δ H^{\circ} = ?$

Molar mass of $C_{2} H_{6} = 30 g {mol}^{- 1}$

$∴ 3 g C_{2} H_{6} = \frac{3}{30} = \frac{1}{10} mol$

$∴$ For formation of $\frac{1}{10} mol C_{2} H_{6}, 8.84 kJ$ heat is liberated.

$∴$ Formation of $1 mol C_{2} H_{6}$ will liberate $88.4 kJ$ of heat.

$∴ Δ_{f} H^{\circ}$ of $C_{2} H_{6} = - 88.4 kJ$

3. ⇒ (MHT CET 2021 20th September Evening Shift )

Calculate heat of formation of $HCl$ gas from following reaction.

$H_{2 (g)} + {Cl}_{2 (g)} \to 2 {HCl}_{(g)}; Δ H = - 194 kJ$

A. $- 143 kJ {mol}^{- 1}$

B. $- 286 kJ {mol}^{- 1}$

C. $- 92 kJ {mol}^{- 1}$

D. $- 97 kJ {mol}^{- 1}$

Correct Option is (D)

$H_{2 (g)} + {Cl}_{2 (g)} \to 2 {HCl}_{(g)}; Δ H = - 194 kJ$

Heat of formation for 2 moles of $HCl = - 194 kJ$

$∴$ Heat of formation for 1 mole of $HCl = - 97 kJ$

4. ⇒ (MHT CET 2021 20th September Evening Shift )

Calculate difference between $Δ H$ and $Δ U$ for following reaction at $25^{\circ} C$ ?

$C_{2} H_{6 (g)} + 3.5 O_{2} \to 2 {CO}_{2 (g)} + 3 H_{2} O_{(l)} (R = 8.314 J K^{- 1} {mol}^{- 1})$

A. $- 9.3 kJ$

B. $- 3.1 kJ$

C. $- 6.2 kJ$

D. $- 16.10 kJ$

Correct Option is (C)

$\begin{aligned} C_{2} H_{6 (g)} + 3.5 O_{2 (g)} \to 2 {CO}_{2 (g)} + 3 H_{2} O_{(l)} \\ Δ n_{(g)} = 2 - 4.5 = - 2.5 \\ Δ H - Δ U = Δ n_{(g)} RT \\ = - 2.5 mol \times 8.314 J K^{- 1} {mol}^{- 1} \times 298 K \\ = - 6193.93 J = - 6.193 kJ \approx - 6.2 kJ \end{aligned}$

5. ⇒ (MHT CET 2021 20th September Morning Shift )

Which of the following reactions shows work of compression?

A. $N H_{3 (g)} + H C l_{(g)} \to N H_{4} C l_{(s)}$

B. $C_{2} H_{6 (g)} \to 2 C_{(s)} + 3 H_{2 (g)}$

C. $2 S O_{3 (g)} \to 2 S O_{2 (g)} + O_{2 (g)}$

D. $2 H_{2} O_{2 (l)} \to 2 H_{2} O_{(l)} + O_{2 (g)}$

Correct Option is (A)

$N H_{3_{(g)}} + H C l_{(g)} \to N H_{4} C l_{(s)}$

In this reaction, gaseous reactants converted into solidified product which resulting in a decrease of volume and shows work of compression.

⇒Thermodynamics