6.9 g of sodium metal dropped 100 g of 13.6 solution of zinc chloride, find the mass fraction of the solution.

| February 1, 2021 | education

As a result of the addition of sodium to the zinc chloride solution (stock solution), free zinc and salt (resulting solution) are formed.
2Na + ZnCl2 = Zn + 2NaCl.
Determine the mass of zinc chloride in solution.
m (ZnCl2) = m (original solution) • W (ZnCl2) / 100% = 100 g • 13.6% / 100% = 13.6 g.
The number of moles of starting materials.
n (ZnCl2) = m / Mr = 13.6 g / 136.3 g / mol = 0.1 mol.
n (Na) = 6.9 g / 23 g / mol = 0.3 mol.
The calculation is based on a disadvantage. The number of moles of reaction products.
n (Zn) = n (ZnCl2) = 0.1 mol.
n (NaCl) = 2 * n (ZnCl2) = 0.2 mol.
Let’s determine the mass of the resulting substances.
m (Zn) = n • Mr = 0.1 mol • 65.4 g / mol = 6.5 g.
m (NaCl) = 0.2 mol * 58.4 g / mol = 11.7 g.
Knowing the masses of all reagents, we determine the mass of the resulting solution.
m (received solution) = m (original solution) + m (Na) – m (Zn) – m (NaCl) = 100 g + 6.9 g – 6.5 g – 11.7 g = 88.7 g.
Mass fraction of substances in the resulting solution.
W (Zn) = m (Zn) / m (obtained solution) • 100% = 6.5 g / 88.7 g • 100% = 7.3%.
W (NaCl) = m (NaCl) / m (obtained solution) • 100% = 11.7 g / 88.7 g • 100% = 13.2%.



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