Question

What minimum amount of H2O (in grams) must be added to an empty, sealed 1.00 L container with normal atmospheric pressure (1.00 atm) to ensure that there is at least some liquid water in it, in addition to the vapor, after the container is heated to 100°C and equilibrium is established. Assume that water vapor approximately obeys the ideal gas law.

Answer 1

Calculate amount of \\'atcr by using ideal gas equation.

Pll = nRT

P= \'apor pressure of \\'ater that equals to I atm

V =\'olun1e of scaled container = 1.00 L

n = Number of moles of \Yater

R= Gas constant = 0.082 L atm K'1mol·1

T= Tempcrarure = 100 •c =373 K

Calculatcb number of moles of \\·atcr by substiruting these values in the above formul

"= Pl' =            (1 atm )(1.00 L )                         = 0.033 mol

RT      (373 K)(0.082 L atm K·1mo1·1)

Minimuim amount of "·ater = Number of moles of \\'ater x Molar mass of "'atcr

= 0.033 mol > 18g mol = 0.60 g Therefore, minimum amoun t of \\'at er is J 0.60 g