Question

How many kJ of heat are released by the reaction of 25.0 g of Na2O2(s) in the following reaction? (M = 78.0 g/mol for Na2O2)

Answer 1

-20.16 KJ of heat are released by the reaction of 25.0 g of Na2O2.

Explanation:

Given:

mass of Na2O2 = 25 grams

atomic mass of Na2O2 = 78 gram/mole

number of mole = $\frac{mass}{atomic mass of 1 mole}$

                          = $\frac{25}{78}$

                          =0. 32 moles

The balanced equation for the reaction:

2 Na2O2(s) + 2 H2O(l) → 4 NaOH(aq) + O2(g) ∆Hο = −126 kJ

It can be seen that 126 KJ of energy is released when 2 moles of Na2O2 undergoes reaction.

similarly 0.3 moles of Na2O2 on reaction would give:

$\frac{126}{2}$ = $\frac{x}{0.32}$

x = $\frac{126 x 0.32}{2}$

 = -20.16 KJ

Thus, - 20.16 KJ of energy will be released.