A solid mixture consists of 27.2 g of KNO_3 (potassium nitrate) and 4.8 g of K_2

Question

A solid mixture consists of 27.2 g of KNO_3 (potassium nitrate) and 4.8 g of K_2SO_4 (potassium sulfate). The mixture is added to 130. g of water. Use this solubility curve (Figure 1) to answer the questions. Crystallization Crystallization is the opposite of dissolution. Since solids tend to dissolve better at higher temperatures, we can cause them to crystallize (i.e., undissolve) from a solution by lowering the temperature. Part B If the solution described in the introduction is cooled to 0 degree C, what mass of KNO_3 should crystallize? Enter your answer numerically in grams. Part C This question will be shown after you complete previous question(s).

Explanation / Answer

From the graph, it shows that 14 g of KNO3 per 100g of water at 0 oC.

So,

(X g of KNO3) / (130 g water) = (14 g of KNO3) / (100 g water)

(X g of KNO3) = (14 g of KNO3) (130 g water) / (100 g water)

(X g of KNO3) = 18.2 g of KNO3

But, we have 27.2 g of KNO3 in 130 g of water at 0 oC and only 18.2 g can dissolve.

So, 27.2 g – 18.2 g = 9 gm (left undissolved which gives the amount that would crystallize).

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