Mass percentage of solution prepared by adding 4 g of a substance in 16 g of water is

To calculate the mass percentage of a solution, you need to follow these steps:

1. First, find the total mass of the solution. This is the sum of the mass of the solute (the substance being dissolved) and the solvent (the substance doing the dissolving). In this case, the total mass is 4 g (substance) + 16 g (water) = 20 g.

2. Next, calculate the mass percentage of the solute. This is the mass of the solute divided by the total mass of the solution, multiplied by 100%. So, the mass percentage of the substance is (4 g / 20 g) * 100% = 20%.

So, the mass percentage of the solution prepared by adding 4 g of a substance in 16 g of water is 20%.