AP Chemistry
4.5 Stoichiometry
A student reacts a sample of pure aluminum metal with an excess of hydrochloric acid according to the following balanced chemical equation:
\[ 2\,\text{Al}(s) + 6\,\text{HCl}(aq) \rightarrow 2\,\text{AlCl}_3(aq) + 3\,\text{H}_2(g) \]
The generated \(\text{H}_2(g)\) is collected over water at \(27^\circ\text{C}\) (\(300\text{ K}\)). The experimental data obtained by the student are recorded in the table below.
Given that the molar mass of \(\text{Al}\) is \(27.0\text{ g/mol}\) and \(R = 0.0821\text{ L}\cdot\text{atm}/(\text{mol}\cdot\text{K})\), what is the percent yield of \(\text{H}_2(g)\) for the reaction?
\[ 2\,\text{Al}(s) + 6\,\text{HCl}(aq) \rightarrow 2\,\text{AlCl}_3(aq) + 3\,\text{H}_2(g) \]
The generated \(\text{H}_2(g)\) is collected over water at \(27^\circ\text{C}\) (\(300\text{ K}\)). The experimental data obtained by the student are recorded in the table below.
| Quantity | Measured Value |
|---|---|
| Mass of \(\text{Al}(s)\) reacted | \(0.0540\text{ g}\) |
| Total barometric pressure | \(780\text{ torr}\) |
| Temperature of gas and water | \(27^\circ\text{C}\) (\(300\text{ K}\)) |
| Volume of wet \(\text{H}_2(g)\) collected | \(59.1\text{ mL}\) |
| Vapor pressure of water at \(27^\circ\text{C}\) | \(20\text{ torr}\) |
Given that the molar mass of \(\text{Al}\) is \(27.0\text{ g/mol}\) and \(R = 0.0821\text{ L}\cdot\text{atm}/(\text{mol}\cdot\text{K})\), what is the percent yield of \(\text{H}_2(g)\) for the reaction?
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