Question

percentage mass of water in na2co3.10h2o

Answer 1

Percentage water is mass of water/mass of compound x 100 
Molar mass of Na2CO3.10H2O is 286 g/mol 
Molar mass of H2O is 18 g/mol so mass of 10H2O is 180 g 
Therefore percentage water is 180/286 x100 = 63%

Answer 2

Answer: Percentage mass of water in $Na_2CO_3.10H_2O$ is 62.9%.

Explanation:

$Mass\%=\frac{\text{Mass of}H_2O}{\text{Mass of} Na_2CO_3.10H_2O}\times 100$

Mass of $H_2O=moles\times {\text {Molar mass}}= 10moles\times 18g/mol=180g$

Mass of $Na_2CO_3=moles\times {\text {Molar mass}}= 1mole\times 106g/mol=106g$

Mass of $Na_2CO_3.10H_2O=106+180= 286g/mol$

$Mass\%=\frac{180}{286}\times 100=62.9\%$