Question

A mixture of caco3 and (nh4)2co3 is 60.7 % co3 by mass. part a find the mass percent of caco3 in the mixture.

Answer 1

The mixture contains:

CaCO3 + (NH4)2CO3 in which the amount of carbonate CO3 = 60.7% by mass

Let, the total mass = 100 grams

Mass of CaCO3 = x grams

Mass of (NH4)2CO3 = y grams

Thus,       x + y = 100 ------------(1)

Mass of CO3 = 60.7% = 60.7 g

Molar mass of CO3 = 60 g/mol

Total # moles of CO3 = 60.7 g/60 g.mol-1 = 1.012 moles

The total moles of CO3 comes from CaCO3 and (NH4)2CO3. Therefore,

moles CaCO3 + moles (NH4)2CO3 = 1.012

mass CaCO3/molar mass CaCO3 + mass (NH4)2 CO3/molar mass = 1.012

x/100 + y/96 = 1.012---------(2)

based on equation 1 we can write: y = 100-x

x/100 + (100-x)/96 = 1.012

x = 71.2 g

Mass of CaCO3 = 71.2 g