In 350 g of water, 4.5 sodium chloride was added after a certain time, part of the water was evaporated.

In 350 g of water, 4.5 sodium chloride was added after a certain time, part of the water was evaporated. Concentrator. salt in the final solution was 5%. How much water has evaporated?

The mass fraction of salt in the initial solution is equal to:
w = m (salt) / (m (water) + m (salt)) * 100% = 4.5 / (350 + 4.5) * 100% = 1.3%.
After some of the water has evaporated:
w = 4.5 / (350 – x + 4.5) * 100% = 5%.
By solving this equation, we find the value of x, which is the mass of water that has evaporated:
4.5 / (354.5 – x) = 5/100.
354.5 – x = 90,
x = 264.5 g.
Therefore, 264.5 g of water evaporated.