Question

取1.43gNa2CO3·xH2O溶于水配成100ml溶液,取1.4

Answer 1

Na2CO3·xH2O=Na2CO3+xH2O

(106+18x)g 106g

1.43 0.530g

解得x=10

(1)n(Na2CO3)=m(Na2CO3)?M(Na2CO3)=0.53g/106g/mol=0.005mol

c(Na2CO3)=n(Na2CO3)/V=0.005mol/0.1L=0.05mol/L

(2)c(Na+)=2c(Na2CO3)=0.1mol/L

(3)由稀释定理c1V1=c2V2有

0.05mol/L*20ml=0.04mol/L*V

V=25ml

V(H2O)=25ml-20ml=5ml