What is the percent by mass of water in the hydrate Na2CO3 * 10H2O (formula mass = 286)?
A. 6.89 %
B. 14.50 %
C. 26.10 %
D. 36.85%
E. 62.90 %
One mole of the hydrate given has a mass of 286. The 10 water moles are part of the hydrate. The water has a mass of 18 g x 10 or 180 g.
Percent of water = 180g (water mass) / 286 (mass of compound) x 100% = 62.9%