A 15% alcohol solution means:

(a) 15 ml alcohol and 85 ml water.

(b) 15 ml alcohol and 100 ml water.

Choose the correct answer.

How much water should be mixed with 12 ml of alcohol so as to obtain 12% alcohol solution?

A 5 per cent sugar solution means that:

(a) 5 g of sugar is dissolved in 95 g of water.

(b) 5 g of sugar is dissolved in 100 g of water.

Choose the correct answer.

Calculate the concentration of a solution which contains 2.5 g of salt dissolved in 50 g of water.

What is the concentration of a solution which contains 16 g of urea in 120 g of solution?