A1.803 g sample of gypsum, a hydrated salt of calcium sulfate, caso4 is heated at a temperature greater than 170 degree celsius in a crucible until a constant mass is reached. the mass of anhydrous caso4 salt is 1.426g. calculate the percent by mass of water in the hydrated calcium sulfate salt.

20.91% of the hydrated calcium sulfate salt is water

Explanation:

Step1 : Calculate the mass of H2O that evaporated

A hydrated salt has a mass of 1.803g. After heating at 170° C, this means water will evaporate, the mass of the salt is 1.426g

The difference is water that evaporated.

⇒Mass H2O of hydration =1.803 g - 1.426g g = 0.377 g H2O

Step 2: Calculate the % of water in the hydrated calcium sulfate salt

⇒ mass of H2O = 0.377g

⇒ mass of calcium sulfate salt = 1.803g

⇒ % water in the calcium sulfate salt = (0.377 / 1.803) x 100% = 20.91%

20.91% of the hydrated calcium sulfate salt is water

1. for the first question, we must find the mass of the anhydrous salt, mgso₄. the molar mass for mgso₄·7h₂o is 246.47 g/mol, while that of mgso₄ is 120.37 g/mol.7.834 g mgso₄·7h₂o * 1 mol mgso₄·7h₂o/246.47 g * 1 mol mgso₄/1 mol mgso₄·7h₂o * 20.37 g mgso₄/mol = 0.647 g mgso₄

2. mass of water = mass of sample - mass of anhydrous salemass of water = 7.834 - 0.647 = 7.19 gpercent water in hydrate = 7.19/7.834 * 100 = 91.74%

your answer is c) plasma

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