Question

Determine the molality of CO2 in soda water at 25 degrees Celsius if the 25.0 g CO2 is dissolved in 125 mL of water. Water has a density of 1.00 g/mL at this temperature

Answer 1

Molar mass of CO2 = 1*MM(C) + 2*MM(O)

= 1*12.01 + 2*16.0

= 44.01 g/mol

mass of CO2 = 25.0 g

we have below equation to be used:

number of mol of CO2,

n = mass of CO2/molar mass of CO2

=(25.0 g)/(44.01 g/mol)

= 0.5681 mol

mass of solvent = 125 g (Since volume is 125 mL and density is 1 g/mL)

= 0.125 kg [using conversion 1 Kg = 1000 g]

we have below equation to be used:

Molality,

m = number of mol / mass of solvent in Kg

=(0.5681 mol)/(0.125 Kg)

= 4.54 molal

Answer: 4.54 molal