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

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}=(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=(1)/(2)*0.0226 \\ mole\text{ of H}_2=0.0113moles \end{gathered}`

According to the ideal gas equation

`\begin{gathered} PV=nRT \\ V=(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=(0.0113*0.08205*298)/(0.974) \\ V=(0.2764)/(0.974) \\ V=0.284L \end{gathered}`

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