HardChemistryHigh School (9–10)GeneralMixtures and Solutions › Mixtures, Solutions and ColloidsNumerical

Potassium nitrate dissolves 169 g in 100 g of water at 80 °C, and 46 g at 30 °C.

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Potassium nitrate dissolves $169\ \text{g}$ in $100\ \text{g}$ of water at $80\ ^\circ\text{C}$ , and $46\ \text{g}$ at $30\ ^\circ\text{C}$ . A saturated solution made with $60\ \text{g}$ of water at $80\ ^\circ\text{C}$ is cooled to $30\ ^\circ\text{C}$ . What mass of crystals forms?

Need a reminder? The key ideaShow

Solubility is the most solute that dissolves in $100\ \text{g}$ of water at a given temperature. A solution that can take no more is saturated. For most solids it rises with temperature; cooling a hot saturated solution makes the extra solid crystallise.

The worked solution

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Work it out on paper first. It is fine to get stuck or make a mistake: that is how we learn. When you are ready, go through the solution one step at a time, and check each step against your own.

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← At 293 K, 36 g of common salt dissolves in 100 g of water to make a saturated solution.Decide whether each is a solution, a colloid or a suspension, and give one reason. →

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