Question

24. The graph below shows the solubility of potassium chloride (KCI) in water. What is the molarity of a saturated aqueous solution of KCI at 20°C? This solution has a density of 1.17 g/mL. 60 50 KCI 20 0 40 Temperature (°C) 60 20 40 30 Solubility (g per 100 g of water)

Answer 1

At 20 deg,in the saturation line, solubility of KCl = 34 g in 100 g of water

mass of KCl= 34 g
total mass of solution 34 g+100 g=134 g

density of solution =1.17 g/ml

volume of solution = mass /density = 134g/1.17 g/ml =114.53 ml

we have molar mass of KCl = 1*39.10 g/mol + 1*35.45 g/mol = 74.55 g/mol
number of mols in 34 g KCl = 34 g/74.55 g/mol=0.456 mols

molarity = number of mols of KCl/total volume = 0.456 mols/0.11453 l = 3.98 M
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