Answer to Question #343066 in Chemistry for soph

Question

8. What is [H3O+] for a 0.500 M solution of hydrochloric acid? Make sure you include the ionization equation. (2 marks)

9. If 2.50g of the strong base lithium hydroxide is dissolved in 1.50 L of solution, what is the concentration of hydroxide ions? Make sure you include the dissociation equation. (3 marks)?

Answer 1

What is [H₃O⁺] for a 0.500 M solution of hydrochloric acid? Make sure you include the ionization equation.

Solution:

Hydrochloric acid (HCl) is a strong acid because it almost completely ionized in water:

HCl(aq) + H₂O(l) → H₃O⁺(aq) + Cl⁻(aq)

And thus a 0.500 M solution of HCl is stoichiometric in H₃O⁺ and Cl⁻, i.e. [H₃O⁺] = [Cl⁻] = 0.500 M

[H₃O⁺] = 0.500 M

If 2.50 g of the strong base lithium hydroxide is dissolved in 1.50 L of solution, what is the concentration of hydroxide ions? Make sure you include the dissociation equation.

Solution:

The molar mass of lithium hydroxide (LiOH) is 23.95 g/mol

Therefore,

Moles of LiOH = (2.50 g LiOH) × (1 mol LiOH / 23.95 g LiOH) = 0.1044 mol LiOH

Molarity = Moles of solute / Liters of solution

Therefore,

Molarity of LiOH solution = (0.1044 mol) / (1.50 L) = 0.0696 mol/L = 0.0696 M

Lithium hydroxide (LiOH) is a strong base because it almost completely ionized in water:

LiOH(aq) → Li⁺(aq) + OH⁻(aq)

And thus a 0.0696 M solution of LiOH is stoichiometric in Li⁺ and OH⁻, i.e. [Li⁺] = [OH⁻] = 0.0696 M

[OH⁻] = 0.0696 M