1.

A 6.90 M Solution of KOH in water contains 30% by mass of KOH. Calculate the density of the KOH solution. (Molar mass of KOH = "56 g mol"^(-1))

Answer»

Solution :6.90 M KOH solution means 6.90 moles of KOH are present in 1 litre of the solution.
But 6.90 moles of KOH `=6.90 xx56 g=386.4g`
Thus, volume of solution containing 386.4 g KOH= 1000 mL
`30%` by mass of KOH solution means that 30 g of KOH are present in 100 g of the solution.
`THEREFORE"Mass of solution containing 386.4 g KOH"=(100)/(30)xx386.4g=1288g`
`therefore"Density of solution "=("Mass")/("Volume")=("1288 g")/("1000 mL")="1.288 g mL"^(-1)`


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