# Calculate the mass of sodium chloride contained in a 200 g solution saturated at 30 ° C

Calculate the mass of sodium chloride contained in a 200 g solution saturated at 30 ° C, if the solubility of the salt at this temperature is 381 g / l of water.

Given:
m solution (NaCl) = 200 g
P ‘(NaCl) = 381 g / l H2O
ρ solution (NaCl) = 1.22 g / ml

To find:
m (NaCl) -?
ω (NaCl) -?
Cm (NaCl) -?

Solution:
1) P ‘(NaCl) = 381 g / l H2O = 381 g / kg H2O;
2) m ‘solution (NaCl) = m’ (NaCl) + m ‘(H2O) = 381 + 1000 = 1381 g;
3) ω ‘(NaCl) = m’ * 100% / m ‘solution = 381 * 100% / 1381 = 27.6%;
4) ω (NaCl) = ω ‘(NaCl) = 27.6%;
5) m (NaCl) = ω * m solution / 100% = 27.6% * 200/100% = 55.2 g;
6) n (NaCl) = m / M = 55.2 / 58.5 = 0.944 mol;
7) V solution (NaCl) = m solution / ρ solution = 200 / 1.22 = 163.934 ml = 0.164 l;
8) Cm (NaCl) = n / V solution = 0.944 / 0.164 = 5.76 M.

Answer: The mass of NaCl is 55.2 g; mass fraction – 27.6%; molar concentration – 5.76 M.

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