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The solubility of a substance in a given solvent is the extent to which that substance dissolves in that solvent. This can be expressed in a wide variety of units: one common way is to state how many grams of solute dissolve in 100 grams of solvent.

solubility = grams of solute/100 grams of solvent
In general, the solubility of a substance is temperature dependant, so solubilities are stated at a given temperature.

Example: At 30 oC, the solubility of potassium nitrate in water is 37.0 g/100 g water. How much potassium nitrate will dissolve in 750 grams of water?

Solution: Simply multiply the solubility of KNO3 and the amount of water- but be careful of the units. The solubility is expressed in terms of 100 grams of water: convert this into grams of water, the unit that the amount of solvent is given in.

Solubility = 37 g KNO3/100 g H2O => 0.37 grams KNO3/1 gram H2O
0.37 g KNO3/1 g H2O * 750 grams H2O = 278 grams KNO3


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