A 1.65 g sample of \(\mathrm{Al}\) reacts with excess \(\mathrm{HCl}\), and the liberated \(\mathrm{H}_{2}\) is collected over water at \(25^{\circ} \mathrm{C}\) at a barometric pressure of \(744 \mathrm{mmHg} .\) What volume of gaseous mixture, in liters, is collected? $$2 \mathrm{Al}(\mathrm{s})+6 \mathrm{HCl}(\mathrm{aq}) \longrightarrow 2 \mathrm{AlCl}_{3}(\mathrm{aq})+3 \mathrm{H}_{2}(\mathrm{g})$$

Short Answer

Expert verified
The corrected volume of the gaseous mixture collected is 2.42 L.

Step by step solution

01

Calculate moles of Al

First, compute for the moles of Al using the given mass and the molar mass of Al, which is \( 26.982 \, g/mol\). Moles of Al \( = \frac{1.65 \, g}{26.982 \, g/mol} = 0.0611 \, mol\)
02

Calculate moles of H2

Determine the moles of \( H_{2} \) using the stoichiometric ratio in the balanced chemical reaction, \( 2Al:3H_{2} = 0.0611 \, mol \, Al:x \, mol \, H_{2}\). Solve for \( x \), getting \( x = \frac{3}{2} \times 0.0611 \, mol \, Al = 0.0916 \, mol \, H_{2}\).
03

Determine the gas volume using the Ideal Gas Law

Use the Ideal Gas Law \(PV = nRT\) where \(P\) is the pressure in atm \(= 744 \, mmHg \times \frac{1 \, atm}{760 \, mmHg} = 0.9789 \, atm\), \(n\) is the number of moles \(= 0.0916 \, mol\), \(R\) is the gas constant \(= 0.0821 \, L.atm/(mol.K)\), and \(T\) is the temperature in Kelvin \(= 25^{\circ} C + 273.15 = 298.15 \, K\). Solving for \(V\), \(V = \frac{nRT}{P}\) gets \(V = \frac{0.0916 \, mol \times 0.0821 \, L.atm/(mol.K) \times 298.15 \, K }{0.9789 \, atm} = 2.30 \, L\).
04

Correct the collected volume for vapor pressure

Lastly, correct for the presence of water vapor in the collected gas. The partial pressure of hydrogen is given by subtracting the water vapor pressure from the total pressure. The vapor pressure of water at \(25^{\circ}C\) is 23.76 mmHg or 0.0313 atm. Hence, the corrected volume of \(H_{2}\) gas is \(V' = nRT/P' = \frac{0.0916 \, mol \times 0.0821 \, L.atm/(mol.K) \times 298.15 \, K }{0.9789 \, atm - 0.0313 \, atm} = 2.42 \, L\).

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