# The decomposition of H_2O_2 produces water and oxygen gas, releasing 197 kJ per one mole of H_2O_2. How much energy is released if we start with 798 grams of H_2O_2?

May 24, 2016

$q = 4629.5 k J$

#### Explanation:

The amount of heat ($q$) released from decomposing $798 g$ of ${H}_{2} {O}_{2}$ could be found by:

$q = \Delta H \times n$ where, $\Delta H$ is the enthalpy of the reaction and $n$ is the number of mole of ${H}_{2} {O}_{2}$.

Note that $\Delta H = 197 k J \cdot m o {l}^{- 1}$

To find $n$, we can simply use: $n = \frac{m}{M M}$ where, $m = 798 g$ is the given mass and $M M = 34 g \cdot m o {l}^{- 1}$ is the molar mass of ${H}_{2} {O}_{2}$.

$n = \frac{m}{M M} = \frac{798 \cancel{g}}{34 \cancel{g} \cdot m o {l}^{- 1}} = 23.5 m o l {H}_{2} {O}_{2}$

Thus, $q = \Delta H \times n = 197 \frac{k J}{\cancel{m o l}} \times 23.5 \cancel{m o l} = 4629.5 k J$