Question

The hydrated salt Na2CO3.xH2O undergoes 63% loss in mass on heating and becomes anhydrous .The value of x is (pls give explanation for necessary steps)

Answer 1

Total mass of hydrated salt Na2CO3.xH2O = (106 + 18x)g out of which 18x is the mass due to water of crystallization.

w(Na2CO3) = 100-63= 37 %;

M (Na2CO3) = 46+12+48 = 106 g/mol;

w(Na2CO3) = M(Na2CO3)/M(Na2CO3*xH2O);

M(Na2CO3*xH2O)= M(Na2CO3)/w(Na2CO3) =106/0.37= 286 g/mol;

M(xH2O) =M(Na2CO3*xH2O)-M(Na2CO3) = 286–106= 180 g/mol;

x =M(xH2O)/M(H2O)= 180/18 = 10.

Answer:10.