Question

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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Answer 1

Answer:

1. Formulae of hydrate is Na₂CO₃.10H₂O

2. Formulae of hydrate is CaSO₄.2H₂O

Explanation:

Q1. Mass of hydrated salt = 8.50 g mass

mass of anhydrous salt = 7.26 grams

mass of water lost = 1.24

Formula of hydrated salt = Na₂CO₃.xH₂O

Formula of anhydrous salt = Na₂CO₃

Molar mass of anhydrous salt is obtained as below where Na = 23, C = 12, O = 16, H = 1

Molar mass of Na₂CO₃ = (23 *2 + 12 + 16 * 3) = 106 g

molar mass of water = (1 *2 + 16) = 18 g

Mole ratio of Na₂CO₃ to H₂O = 7.26/106 : 1.24/18

Mole ratio of Na₂CO₃ to H₂O = 0.0068 : 0.068

Mole ratio of Na₂CO₃ to H₂O = 1 :10

Therefore, formulae of hydrate is Na₂CO₃.10H₂O

Q2.  Mass of hydrated salt = 60.98 g mass

mass of anhydrous salt = 48.23 grams

mass of water lost = 12.75

Formula of hydrated salt = CaSO₄.xH₂O

Formula of anhydrous salt = CaSO₄

Molar mass of anhydrous salt is obtained as below where Ca = 40, S = 32, O = 16, H = 1

Molar mass of CaSO₄= (40 + 32 + 16 * 4) = 136 g

molar mass of water = (1 *2 + 16) = 18 g

Mole ratio of CaSO₄ to H₂O = 48.23/136 : 12.75/18

Mole ratio of CaSO₄ to H₂O = 0.35 : 0.70

Mole ratio of CaSO₄ to H₂O = 1 : 2

Therefore, formulae of hydrate is CaSO₄.2H₂O

Answer 2

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