A weighed portion of magnesium oxide weighing 8 g was treated with a 20% hydrochloric acid solution weighing

A weighed portion of magnesium oxide weighing 8 g was treated with a 20% hydrochloric acid solution weighing 146 g. Calculate: a) the mass of the formed salt, b) the mass fraction of the formed salt in the resulting solution.

Given:
m (MgO) = 8 g
ω (HCl) = 20%
m solution (HCl) = 146 g

Find:
m (salt) -?
ω (salt) -?

Solution:
1) MgO + 2HCl => MgCl2 + H2O;
2) n (MgO) = m / M = 8/40 = 0.2 mol;
3) m (HCl) = ω * m solution / 100% = 20% * 146/100% = 29.2 g;
4) n (HCl) = m / M = 29.2 / 36.5 = 0.8 mol;
5) n (MgCl2) = n (MgO) = 0.2 mol;
6) m (MgCl2) = n * M = 0.2 * 95 = 19 g;
7) m2 solution = m (MgO) + m solution (HCl) = 8 + 146 = 154 g;
8) ω (MgCl2) = m * 100% / m2 solution = 19 * 100% / 154 = 12%.

Answer: The mass of MgCl2 is 19 g; mass fraction – 12%.