Lithium metal dissolves in water to yield hydrogen gas and aqueous lithium hydroxide. What is the final concentration of hydroxide ions when 5.500 g of lithium metal is dropped into 750. mL of water
A) 1.06 M
B) 0.528 M
C) 2.11 M
D) 0.792 M
E) 0.943 M

Question

Quizplus · Accepted Answer

Lithium reacts with water in a 2:2 ratio to form lithium hydroxide and hydrogen gas. The molar mass of lithium is approximately 6.94 g/mol, so 5.500 g of lithium is about 0.792 mol. Since the reaction ratio is 2:2, this produces 0.792 mol of hydroxide ions in 750 mL (or 0.75 L) of water, resulting in a concentration of $ \frac{0.792 \, \text{mol}}{0.75 \, \text{L}} = 1.056 \, \text{M} $, which rounds to 1.06 M.

Lithium Metal Dissolves in Water to Yield Hydrogen Gas and Aqueous