In 400 g of a solution with a mass fraction of r. Substance of 20 percent, 40 g of salt was added.

In 400 g of a solution with a mass fraction of r. Substance of 20 percent, 40 g of salt was added. Determine the mass fraction of salt in the resulting solution.

1. Given: 400 g of a 20% solution. Let’s find the mass of the dissolved salt by the formula:

m (salt) = m (solution) * w (solution) / 100% = 400 * 20/100 = 80 g

2. Given: Added 40 g of salt. Let’s find the total mass of salt:

80 + 40 = 120 g

3. Find the total mass of the solution:

400 + 40 = 440 g

4. Let’s calculate the mass fraction of salt in the resulting solution by the formula:

w (solution) = m (salt) * 100% / m (solution) = 120 * 100/440 = 27.3%.