The heat of combustion of ethane (C2H6) is -337.0 kcal at 25°C. The heat of the reaction when 3 g of ethane is burnt will be:

Explanation

Option C is correct.The heat of combustion of ethane (C2H6) is -337.0 kcal at 25°C. This means that 337.0 kcal of heat is released when 1 mole of ethane is burned in oxygen. The heat of combustion of ethane is a state function, which means that it depends only on the initial and final states of the system, and not on the path taken. In this case, the initial state is 3 g of ethane and the final state is the products of combustion, which are carbon dioxide and water. The heat of the reaction when 3 g of ethane is burnt is -33.7 kcal. This is less than the heat of combustion of 1 mole of ethane, because only 3 g of ethane is burned. The heat of the reaction can be calculated using the following equation: Heat of reaction = Heat of combustion × Mass of ethane / Molar mass of ethane Substituting the values from the previous equations, we get: Heat of reaction = -337.0 kcal × 3 g / 30.07 g/mol Heat of reaction = -33.7 kcal Therefore, the heat of the reaction when 3 g of ethane is burnt is -33.7 kcal.