ICSE Class 9 Chemistry Question 29 of 31

Water — Question 6

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6
Question

Question 4(b)

What weight of sodium nitrate will separate when a saturated solution containing 50 gram of water is cooled from 50°C to 30°C ? The solubility of NaNO3 at 50°C and 30°C is 114 g and 86 g respectively.

Answer

Given,
Mass of solvent = 50 g

Solubility of NaNO3 at 50°C = 114 g

Solubility of NaNO3 at 30°C = 86 g

Solubility = Mass of soluteMass of solvent\dfrac{\text{Mass of solute}}{\text{Mass of solvent}} x 100

Rearranging the above equation

Mass of solute = Solubility x Mass of solvent100\dfrac{\text{Solubility x Mass of solvent}}{100}

∴ Mass of solute at 50°C = 114100\dfrac{114}{100} x 50

= 57 g

∴ Mass of solute at 30°C = 86100\dfrac{86}{100} x 50

= 43 g

∴ Amount of NaNO3 that separate = 57 g - 43 g = 14 g