Answer :
When a 130-gram saturated solution of sodium nitrate is cooled from 30 degrees to 20 degrees Celsius, 7 grams of sodium nitrate will crystallize out due to the difference in solubility at these temperatures. Option A.
The solubility of a substance refers to the maximum amount of that substance that can dissolve in a certain amount of solvent at a given temperature.
In this case, the solubility of sodium nitrate at 20°C and 30°C is given as 88 grams and 95 grams respectively.
If a 130-gram saturated solution of sodium nitrate is cooled from 30 degrees to 20 degrees Celsius, the amount of sodium nitrate that can stay dissolved in the solution decreases.
Therefore, the extra sodium nitrate will crystallize out. The difference in solubility at 30°C and 20°C is 95 - 88 = 7 grams. So, 7 grams of sodium nitrate will crystallize out of the solution when cooled from 30 degrees to 20 degrees Celsius.
Therefore, option A) 7 grams of sodium nitrate will crystallize out is the correct answer.
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