Question

What volume of hydrogen gas is evolved from a reaction between 0.52 g of Na and water? The gas is collected at 25°C and 740 mmHg.___ Na (s) + ___ H2O (l) → ___NaOH (aq) + ___ H2 (g)

Answer 1

Answer:

0.284L

Explanations

The balanced chemical reaction between sodium and water is expressed as:

$2Na(s)+2H_2O(l)\rightarrow2NaOH(aq)+H_2(g)$

Determine the moles of sodium Na that reacted

$\begin{gathered} moles\text{ of Na}=\frac{mass}{molar\text{ mass}} \\ moles\text{ of Na}=\frac{0.52}{23} \\ moles\text{ of Na}=0.0226moles \end{gathered}$

Based on stoichiometry, 2moles of sodium produces 1 mole of hydrogen gas. The moles of hydrogen gas required is given as:

$\begin{gathered} mole\text{ of H}_2=\frac{1}{2}\times0.0226 \\ mole\text{ of H}_2=0.0113moles \end{gathered}$

According to the ideal gas equation

$\begin{gathered} PV=nRT \\ V=\frac{nRT}{P} \end{gathered}$

Given the following

P = 740mmHg = 0.974atm

T = 25 +273 = 298K

R = 0.08205 Latm/molK (Gas constant)

Substitute the given parameters into the formula to have:

$\begin{gathered} V=\frac{0.0113\times0.08205\times298}{0.974} \\ V=\frac{0.2764}{0.974} \\ V=0.284L \end{gathered}$

Hence the volume of hydrogen gas that evolved from the reaction is 0.284L