Question

When a sample of aluminum is reacted with hydrochloric acid, 355mL of dry hydrogen gas is collected. The pressure of the gas is 756.3torr and the temperature is 35.0°C. Determine the mass of aluminum in the sample.

Answer 1

To determine the mass of aluminum in the sample, use the balanced equation for the reaction between aluminum and hydrochloric acid. Convert pressure and temperature, calculate the number of moles of hydrogen gas using the ideal gas law, use the mole ratio to determine the number of moles of aluminum, and convert moles of aluminum to mass using the molar mass of aluminum. The mass of aluminum in the sample is approximately 0.273 grams.

Step-by-step explanation:

To determine the mass of aluminum in the sample, we can use the balanced equation for the reaction between aluminum and hydrochloric acid, which is:

2 Al(s) + 6 HCl(aq) → 2 AlCl3(aq) + 3 H2(g)

From the equation, we can see that 2 moles of aluminum produces 3 moles of hydrogen gas. Using the ideal gas law, we can calculate the number of moles of hydrogen gas produced from the given pressure and temperature.

Then, we can use the mole ratio to determine the number of moles of aluminum present in the sample. Finally, we can convert moles of aluminum to mass using the molar mass of aluminum.

Let's calculate:

Convert pressure from torr to atm: 756.3 torr = 0.995 atm

Convert temperature from Celsius to Kelvin: 35.0°C = 308.15 K

Calculate the number of moles of hydrogen gas using the ideal gas law: n(H2) = (PV) / (RT)

= (0.995 atm) * (0.355 L) / ((0.0821 L·atm/(mol·K)) * (308.15 K))

= 0.01519 mol H2

Use the mole ratio from the balanced equation to determine the number of moles of aluminum: n(Al) = (2/3) * n(H2)

= (2/3) * 0.01519 mol

= 0.01013 mol Al

Convert moles of aluminum to mass: m(Al) = (0.01013 mol) * (26.98 g/mol)

= 0.273 g

Therefore, the mass of aluminum in the sample is approximately 0.273 grams.