Answer to Question #332606 in General Chemistry for Ivan Ackerman

Question

What are the concentrations of OH− and H+ (H+ is short for H3O+) in a 0.00070 M solution of Ba(OH)2 at 25 °C? Assume complete dissociation.

Answer 1

Solution:

Ba(OH)₂ is the strong base that completely dissociates into barium (Ba²⁺) and hydroxide (OH⁻) ions.

The dissociation equation for Ba(OH)₂ in aqueous solution is:

Ba(OH)₂ → Ba²⁺ + 2OH⁻

From the reaction, one barium ion and two hydroxide ions are formed.

So, the concentration of OH⁻ is two times the concentration of Ba(OH)₂

Therefore,

[OH⁻] = 2 × C_M(Ba(OH)₂) = 2 × (0.00070 M) = 0.0014 M

[OH⁻] = 0.0014 M

K_w = [H⁺] × [OH⁻] = 1.0×10⁻¹⁴

Therefore,

[H⁺] = K_w / [OH⁻] = (1.0×10⁻¹⁴) / (0.0014) = 7.14×10⁻¹²

[H⁺] = 7.14×10⁻¹² M

Answer:

[OH⁻] = 0.0014 M

[H⁺] = 7.14×10⁻¹² M