Chemical Thermodynamics Chapter 4 Chemistry Class 12 Textbook Solution

Given: \( \Delta_r H^\circ = -1200 \, \text{kJ} \), Mass of CO = 12 g

To find: Heat evolved when 12g of CO reacts with NO₂

Calculation:

According to the given reaction, 1200 kJ of heat is evolved when 4 moles of CO react with NO₂. So the heat evolved per mole is \( \frac{1200 \, \text{kJ}}{4 \, \text{mol}} = 300 \, \text{kJ mol}^{-1} \)

Molar mass of CO = 12 + 16 = 28 g mol\(^{-1}\)

Number of moles of CO = \( \frac{\text{Mass of CO}}{\text{Molar mass of CO}} = \frac{12 \, \text{g}}{28 \, \text{g mol}^{-1}} = 0.4286 \, \text{mol} \)

So, heat evolved when 0.4286 moles of CO reacts

\( = 0.4286 \, \text{mol} \times 300 \, \text{kJ mol}^{-1} = 128.58 \, \text{kJ} \)

The heat evolved when 12 g of CO reacts with NO₂ is 128.58 kJ.