Page 252 - Chemistry eBook
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Another Percent Composition of Hydrates Problem
The mass of a crucible (container) + the cover = 11.7 grams.
The mass of the crucible + cover + hydrated crystal = 14.9 grams.
The mass of the crucible +cover + hydrated crystal + anhydrate crystal = 14.53 grams. What is the percent mass of water in the hydrated crystal?
Answer:
1. To find the mass of the water: Subtract the anhydrated crystal (crystal without
water) from the hydrated crystal (crystal with water). Hydrate without crucible and cover: 14.9 – 11.7 = 3.2 Anhydrate without crucible and cover: 14.53 – 11.7 = 2.83 3.2 – 2.83 = 0.37 (Mass of part)
2. Plug into equation: 0.37 × 100 = 11.6% 3.2
251 © UNIT 6: MATH IN CHEMISTRY
