How much water must be evaporated from 500 g of 5% sodium chloride solution to convert it into physiological saline?

Given: m (solution) = 500 g, ω (salt) = 5%, or 0.05, ωph (salt) = 0.09.
Find: mw (water) -?
Decision.
1. Calculate the mass of the solute (salt) in the original solution:
m (salt) = m (solution) • ω (salt) = 500 g • 0.05 = 25 g.
2. Calculate the mass of water in the original solution:
m (water) = m (solution) -m (salt) = 500 g – 25 g = 475 g.
3. Calculate the mass of saline:
mph (solution) = m (salt): ωph (salt) = 25 g: 0.09 = 277.8 g.
4. Find the mass of water that needs to be evaporated:
mw (water) = m (water) -mph (water) = 475 g – 277.8 g = 197.2 g.
Answer: 197.2 g.

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