2.5 g of sodium chloride was dissolved in 250 g of water. Determine the mass fraction of salt in the resulting solution.

Given: m (water) = 250 g, m (salt) = 2.5 g.
Find: ω (salt) -?
Decision.
1. Find the mass of the solution:
m (solution) = m (salt) + m (water) = 2.5 g + 250 g = 252.5 g.
2. Find the mass fraction of the dissolved substance (salt):
ω (salt) = m (salt) / m (solution) = 2.5 g: 252.5 g = 0.0099, or,
multiplying this value by 100%, we get 0.99%.
Answer: 0.99%.

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