Question

the reaction of sodium(s) with water(l) to form sodium hydroxide(aq) and hydrogen(g) proceeds as follows: 2na(s) + 2h₂o(l)→2naoh(aq) + h₂(g). when 4.62 g na(s) reacts with sufficient h₂o(l), 37.1 kj is evolved. calculate the value of δᵣh for the chemical equation given. kj/mol

Explanation:

Step1: Calculate moles of Na

The molar mass of Na is $M_{Na}=22.99\ g/mol$. The number of moles $n$ of Na is calculated using the formula $n=\frac{m}{M}$, where $m = 4.62\ g$. So, $n=\frac{4.62\ g}{22.99\ g/mol}\approx0.201\ mol$.

Step2: Calculate $\Delta H$ per mole

We know that when $n = 0.201\ mol$ of Na reacts, $37.1\ kJ$ of heat is evolved. The molar - enthalpy change $\Delta H$ is calculated using the proportion $\Delta H=\frac{q}{n}$, where $q=- 37.1\ kJ$ (negative because heat is evolved). So, $\Delta H=\frac{-37.1\ kJ}{0.201\ mol}\approx - 184.6\ kJ/mol$.

Answer:

$-184.6\ kJ/mol$