A 6.90 M KOH solution in water has 30% by weight of KOH. The density of KOH solution is:
Here, we have 6.90 M solution of KOH. It contains 6.9 mol of KOH in 1000 cm3 of solution.
Mass of 6.90 mol of KOH=6.90×(39+16+1) g=386.4 g
Again, a 30 solution contains 30 g of KOH in 100 g of solution. Therefore, 386.4 g of KOH is present in =10030×386.4=1288 g of solution
So, density of KOH solution =MassVolume=12881000=1.288 g/cm3
Hence, this is the required answer.