Question

Calcium carbonate is know to react to form CO2 according to the following reaction: CaCO3 + 2H+ → Ca2+ + H2O + CO2 Use the Ideal Gas law to calculate the mass of CaCO3 required to generate 300 torr of pressure at standard temperature in a 50.0 mL flask

Answer 1

1st calculate the mol of CO2 formed

Given:

P = 300.0 torr

= (300.0/760) atm

= 0.3947 atm

V = 50.0 mL

= (50.0/1000) L

= 0.05 L

T = 273.0 K

find number of moles using:

P * V = n*R*T

0.3947 atm * 0.05 L = n * 0.08206 atm.L/mol.K * 273 K

n = 8.81*10^-4 mol

From reaction,

mol of CaCO3 reacting = mol of CO2 formed

= 8.81*10^-4 mol

Molar mass of CaCO3,

MM = 1*MM(Ca) + 1*MM(C) + 3*MM(O)

= 1*40.08 + 1*12.01 + 3*16.0

= 100.09 g/mol

use:

mass of CaCO3,

m = number of mol * molar mass

= 8.81*10^-4 mol * 1.001*10^2 g/mol

= 8.818*10^-2 g

Answer: 8.82*10^-2 g