Question 3 (1 point) If a 8.50 grams of a hydrate of sodium carbonate, Na2CO3, is heated so that the mass then becomes 7.26 grams, what is the correct formula of
the hydrate? Na2CO3 _H20
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Question 4 (1 point)
Which is the formula for a hydrate of calcium sulfate, CaSO4, that had a mass of 60.98 grams before heating and 48.23 grams after heating?
CaSO4
_H20
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Explanation:

Question 3:

Mass of anhydrous compound = 7.26g

Mass of water = 8.50 - 7.26 = 1.24 g

Percentage of water of crystallization in the compound is = (1.24 / 8.50) * 100 = 14.59%

The mass ratio of Na2CO3 : H2O = 7.26 : 1.24

Using mole = mass / molar mass;

The mole ratio of  Na2CO3 : H2O = 7.26 /105.99  : 1.24 / 18 = 0.069 : 0.069 or 1 : 1

The formular is; Na2CO3.H2O

Question 4:

Mass of anhydrous compound = 48.23 g

Mass of water = 60.98 - 48.23 = 12.75 g

Percentage of water of crystallization in the compound is = (12.75 / 60.98) * 100 = 20.91%

The mass ratio of CaSO4 : H2O = 48.23 : 12.75

Using mole = mass / molar mass;

The mole ratio of  CaSO4 : H2O = 48.23 / 136.14 : 12.75 / 18 = 0.3543 : 0.708 which is 1 : 2

The formular is; CaSO4.2H2O

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