Question

For the following reaction given bellow, calculate how much heat will be released when 8 g of hydrogen reacts. (1 mole of $H_2$ weighs approximately 2 grams.)
$2H_2\left(g\right)+O_2\left(g\right)\to 2H_{2}O\left(g\right)$
$\Delta H=-115.60kcal$

• A. 57.8 kcal
• B. 115.6 kcal
• C. 173.4 kcal
• D. 231.2 kcal
• E. 462.4 kcal

Answer 1

The correct option is D 231.2 kcal

$2H_2+O_2\to 2H_{2}O$; $\Delta H_{reaction}=-115.6kcal$
In this reaction the weight of $H_2$ gas = 4 g.
Now, for 8 g of $H_2$ gas the above reaction and enthalpy of the reaction must be multiplied by 2.
$2\times [2H_2+O_2\to 2H_{2}O];$ $2\times \Delta H_{reaction}=2\times (-115.6)=231.2kcal$