Question

When 2 moles of Na(s) react with H2O(l) to form NaOH(aq) and H2(g) according to the following equation, 369 kJ of energy are evolved. 2Na(s) + 2H2O(l)2NaOH(aq) + H2(g) Is this reaction endothermic or exothermic? What is the value of q? kJ g

Answer 1

Answer:

Exothermic

q = -8.03 kJ/g

Explanation:

When 2 moles of Na(s) react with H₂O(l) to form NaOH(aq) and H₂(g) according to the following equation, 369 kJ of energy are evolved.

The thermochemical equation is:

2 Na(s) + 2 H₂O(l) → 2 NaOH(aq) + H₂(g)    ΔH = -369 kJ

Since the energy is evolved, the reaction is exothermic, which is why the enthalpy of the reaction (ΔH) is negative.

The heat released (q) per gram of Na(s) is (molar mass 22.98 g/mol):

$\frac{-369kJ}{2molNa} .\frac{1molNa}{22.98gNa} =-8.03kJ/g$