Calculate the mass fraction of potassium sulfide in 200 g of an aqueous solution

| February 13, 2021 | education

Calculate the mass fraction of potassium sulfide in 200 g of an aqueous solution if it is known that it has completely reacted with 248.25 g of a 20% solution of lead nitrate.

1. K2S + Pb (NO3) 2 = PbS + 2KNO3;

2.Calculate the mass of dissolved nitrate:

m (Pb (NO3) 2) = (w * m (Pb (NO3) 2 solution)): 100% = (248.25 * 20): 100% = 49.65 g;

3. find the amount of reactants:

M (Pb (NO3) 2) = 207 + 2 * 14 + 3 * 2 * 16 = 331 g / mol;

n (Pb (NO3) 2) = m: M = 49.65: 331 = 0.15 mol;

n (K2S) = 0.15 mol;

4. Find the mass of potassium sulfide:

M (K2S) = 39 * 2 + 32 = 110 g / mol;

m (K2S) = 0.15 * 110 = 16.5 g;

5.Calculate the mass concentration of sulfide in the initial solution:

w (K2S) = (m (K2S): m (K2S solution)) * 100% = (16.5: 200) * 100% = 8.25%.

Answer: 8.25%



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