Question

A chemist reacts magnesium with hydrochloric acid and collects 57.48 mL of the hydrogen gas that is produced by water displacement. If the lab temperature is 24 C and the atmospheric pressure is 742.1 mm Hg, how many grams of hydrogen are produced? Water vapor pressure is 22.4 mm Hg at 24 C.

Answer 1

Answer:

0.00446 grams of hydrogen are produced.

Explanation:

Atmospheric pressure at which hydrogen gas was collected = p= 742.1 mmHg

Vapor pressure of the hydrogen gas = p' = 22.4 mmHg

Pressure of the hydrogen gas = P

$p=p'+P$

P = p - p' = 742.1 mmhg - 22.4 mmhg = 719.7 mmHg

719.7 mmHg = $\frac{719.7}{760} atm= 0.947 atm$

1 atm = 760 mmHg

Volume of the hydrogen gas ,V = 57.48 mL = 0.05748 L

1 mL =0.001 L

Temperature of the hydrogen gas = T = 24°C=24+ 273 K = 297 K

Moles of hydrogen gas = n

$PV=nRT$ ( Ideal gas equation)

$n=\frac{PV}{RT}=\frac{0.947 atm\times 0.05748 L}{0.0821 atm L/mol K\times 297 L}$

n = 0.00223 mol

Mass of 0.00223 moles of hydrogen gas:

0.00223 mol × 2 g/mol = 0.00446 g

0.00446 grams of hydrogen are produced.