CaC2 (s) + 2H2O (l) → C2H2 (g) + Ca (OH) 2 (s).

Suppose this reaction takes place in a sealed container in which the gas occupies a volume of 1.50 liters. The container is kept at a temperature of 0°C. If 5.18 grams of calcium carbide reacts with excess water, what is the partial pressure of the ethyne gas produced, in atmospheres?

The partial pressure of the ethyne is 1.21 atmospheres.

Explanation:

The molar mass of calcium carbide is 64.100 grams/mole. Convert the amount of calcium carbide from grams to moles:

5.18 g * = 0.0808 mol CaC2.

The ratio of calcium carbide to ethyne is 1 : 1, so 0.0808 mol of ethyne is produced.

Use the ideal gas law to find the pressure after converting the temperature to kelvins:

0°C + 273.15 = 273 K.

Now solve the ideal gas law formula for pressure:

PV = nRT

P =

The answer needs to be in atmospheres, so use

R = 0.0821 L atm/mol K:

P =

= 1.21 atm