Determine the mass fraction of lithium hydroxide in a solution obtained by dissolving 30 g of lithium oxide in 150 g of water.

Let’s execute the solution:
1. We write down the equation according to the condition:
m = 30 g m = 150 g W -?
Li2O + H2O = 2LiOH – lithium hydroxide obtained;
2. Calculation of molar masses:
M (Li2O) = 29.8 g / mol;
M (LiOH) = 23.9 g / mol.
3. Determine the amount of the original substance:
Y (Li2O) = m / M = 30 / 29.8 = 1 mol.
4. Proportion:
1 mol (Li2O) – X mol (LiOH);
-1 mol -2 mol hence, X mol (LiOH) = 1 * 2/1 = 2 mol.
5. Find the mass of the product:
m (LiOH) = Y * M = 2 * 23.9 = 47.8 g.
6.Calculate the mass fraction of the product in the solution:
W = m (substance) / m (solution) * 100;
W = 47.8 / 150 * 100 = 31.86%
Answer: the mass fraction of lithium hydroxide in the solution is 31.86%.