Question

A calorimeter that measures an exothermic heat of reaction by the quantity of ice that can be melted is called an ice calorimeter. Consider a reaction in which 0.00400 mol of methane gas, CH4 (g), is burned completely at constant pressure in the presence of excess air. The heat liberated from the reaction melted 10.7 g of ice at 0 degrees celcius (the heat required to melt the ice (heat of fusion) is 333.5 J/g). What is the change in enthalpy for this reaction?

Answer 1

Answer:

-892.1 kJ/mol is the change in enthalpy for this reaction.

Explanation:

The heat required to melt the ice or heat of fusion =$\Delta H_{fus}=333.5 J/g$

Mass of an ice = 10.7 g

Amount of heat required to melt 10.7 grams of ice at 0 degrees Celsius: Q

$Q=10.7 g\times 333.5 J/g=3,568.45 J$

$CH_4+2O_2\rightarrow CO_2+2H_2O$, ΔH = ?

Heat released on combustion of 0.00400 moles of methane = Q'= -Q

Q' = -3,568.45 J = -3.568 kJ ( 1J = 0.001 kJ)

Change in enthalpy for this reaction = ΔH

$\Delta H=\frac{Q'}{0.00400 mol}=\frac{-3.568 kJ}{0.00400 mol}=-892.1 kJ/mol$

-892.1 kJ/mol is the change in enthalpy for this reaction.