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A 6.40M solution of KOH in water contains 30% by mass of KOH Calculate density of KOH solution ( |
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Answer» The molecular weight of potassium hydroxide, KOH = 56 g/mol Molarity (M) of a solution is defined as the moles per unit volume of a substance. Thus, if we have 1 L of solution, we have 6.9 moles of potassium hydroxide in a 6.9 M solution. This is also equal to 386.4 g (= 56 g/mol x 6.9 mol) of potassium hydroxide in 1 L of solution. Since potassium hydroxide makes up only 30% of the solution, the actual mass of the solution is: mass of solution = 386.4 g / (30/100) = 1,288 g The density of a substance is the ratio of mass to its volume. Here we have a solution that has a mass of 1,288 g and a volume of 1 L. Thus the density of such a solution is: density = mass / volume = (1,288 g / 1 L) =1,288 g/Lor1.288 kg/L |
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