Answer to Question #349491 in General Chemistry for hailey

Question

An aqueous solution of H 2 S is added to an aqueous solution of NaOH and a reaction occurs. 3.7x10 -

4 mol of OH –1 ions are measured in the 550mL solution, calculate the number of moles of H 3 O +1 ions.

Remember, Molarity = mol/L. Calculate the concentration of the H + ions. Is the solution more acidic

or basic?

Answer 1

Solution:

Molarity = Moles / Liters of solution

Moles of OH^− ions = 3.7×10^−4 mol

Liters of solution = (550 mL) × (1 L / 1000 mL) = 0.55 L

Therefore,

[OH^−] = (3.7×10^−4 mol) / (0.55 L) = 6.73×10^−4 M

We can convert between [OH^−] and pOH using the following equations:

pOH = −log[OH^−]

pOH = −log(6.73×10^−4) = 3.17

pOH = 3.17

For any aqueous solution at 25^∘C:

pH + pOH = 14

pH = 14 − pOH = 14 − 3.17 = 10.83

pH = 10.83

Any solution that has a pH greater than 7 is considered basic

We can convert between pH and [H⁺] using the following equations:

[H⁺] = 10^−pH

[H⁺] = 10^−10.83 = 1.48×10^−11

[H⁺] = 1.48×10^−11 M

H⁺ = H₃O⁺

[H₃O⁺] = [H⁺] = 1.48×10^−11 M

Moles of H₃O⁺ ions = [H₃O⁺] × Liters of solution

Moles of H₃O⁺ ions = (1.48×10^−11 M) × (0.55 L) = 8.14×10^−12 mol

Moles of H₃O⁺ ions = 8.14×10^−12 mol

Answer:

The number of moles of H₃O⁺ ions is 8.14×10^−12 mol

The concentration of hydrogen ions (H⁺) is 1.48×10^−11 M

The solution is basic