1.84 gram of a mixture of calcium carbonate and magnesium carbonate is strongly heated till no further loss of mass takes place. The residue weights 0.96 g. Calculate the percentage composition of mixture.

CaCO₃     ?    CaO + CO₂

100gms            56g     44g

 

1. 100gm CaCO₃ forms 56 gms CaO

X gm CaCO₃ forms 56.x/100 = 0.56x gm CaO

 

2. MgCO₃     ?    MgO+ CO₂

    84g                  40g    44g

 

84g MgCO₃ forms 40g MgO 

Therefore, (1.84 - x)g of MgCO₃ forms 40 x (1.84 - x) / 84 g MgO                                                       

 

Total Mass of Cao + MgO from the above 

= 0.56x + 40 x (1.84 - x) / 84 = 0.96g (given)

 

Hence, x = 1

Mass of CaCO₃ = 1gm

Mass of MgCO₃ = (1.84 - 1)

                       = 0.84g

 

Percentage of CaCO₃ in the mixture = 1 x 100 / 1.84

                                                     = 54.35%

 

Percentage of MgCO₃ in the mixture = 100 - 54.35 = 45.65%