The mass fraction of magnesium chloride in a solution obtained by dissolving 5 grams of it in 115 grams of water is …

m (MgCl2) = 5 g.
m (H2O) = 115 g.
Determine the mass fraction of magnesium chloride. We write down the solution.
To solve the problem, we use the following formula.
W = m r.v / m r-ra * 100%.
Where m p. in. is the mass of the solute.
m solution is the mass of the solution.
W is the mass fraction of the substance.
We find the mass of the solution.
m = m r.v + m H2O = 5 + 115 = 120 g.
We find the mass fraction of magnesium chloride.
W = 5/120 * 100% = 4.2%.
This means that the mass fraction of magnesium chloride in the resulting solution is 4.2 percent.
Answer: W = 4.2%.