Question

Consider the reaction:

Answer 1

Answer: The formation of given amount of oxygen gas results in the absorption of 713 kJ of heat.

Explanation:

To calculate the number of moles, we use the equation:

$\text{Number of moles}=\frac{\text{Given mass}}{\text{Molar mass}}$

Given mass of oxygen gas = 83 g

Molar mass of oxygen gas = 32 g/mol

Putting values in above equation, we get:

$\text{Moles of oxygen gas}=\frac{83g}{32g/mol}=2.594mol$

For the given chemical equation:

$2Fe_2O_3\rightarrow 4Fe+3O_2;\Delta H^o_{rxn}=+824.2kJ$

Sign convention of heat:

When heat is absorbed, the sign of heat is taken to be positive and when heat is released, the sign of heat is taken to be negative.

By Stoichiometry of the reaction:

When 3 moles of oxygen gas is formed, the amount of heat absorbed is 824.2 kJ

So, when 2.594 moles of oxygen gas is formed, the amount of heat absorbed will be = $\frac{824.2kJ}{3mol}\times 2.59mol=713kJ$

Hence, the formation of given amount of oxygen gas results in the absorption of 713 kJ of heat.