A

To find the value of H in the equation given, we need to account for the heat exchange between steam and water during the phase change and cooling process.
Step 1: Calculate the heat lost by steam as it condenses to water and cools down from 200ºC to 100ºC.
Step 2: Use the formula: \( Q = m \cdot L + m \cdot c \cdot \Delta T \)
where \( m \) is mass, \( L \) is the latent heat of vaporization, \( c \) is the specific heat, and \( \Delta T \) is the change in temperature.
The latent heat of vaporization for water is approximately 540 cal/g.
For 1 kg of steam, \( m = 1000 g \).
Heat loss during condensation: \( Q_{condensation} = m \cdot L = 1000 g \cdot 540 \text{ cal/g} = 540000 ext{ cal} \)
After condensation, the steam becomes water at 100ºC. Thus, no temperature change occurs after cooling.
The heat lost from the steam equals the heat gained by water (which is initially at 100ºC) and this provides the value of H:
Therefore, \( H = 540000 ext{ cal} + 0 = 540000 ext{ cal} \)
The value of H is 540000 cal.