Calculate either [H3O+] or [OH−] for each of the solutions.

Question

Solution A: [OH−]=1.51×10−7 M; [H3O+]=

Solution B: [H3O+]=9.55×10−9 M; [OH−]=

Solution C: [H3O+]=7.07×10−4 M; [OH−]=



Which of these solutions are basic at 25 °C?

Solution A: [OH−]=1.51×10−7 M

Solution B: [H3O+]=9.55×10−9 M

Solution C: [H3O+]=7.07×10−4 M

Answer 1

Rose,

You need to know certain equations/formulas/relationships in order to calculate [H₃O⁺] and [OH^-]:

[H₃O⁺][OH^-] = 1x10^-14 = Kw (ionization constant for H₂O)

Solution is acidic if [H₃O⁺] is greater than 1x10^-7 M and basic if it is less than 1x10^-7 M

Solution is basic if [OH-] is greater than 1x10^-7 M and acidic if it is less than 1x10^-7 M

Solution A: [OH^-] = 1.51x10^-7 M

Solving for [H₃O⁺] we have ...

[H₃O⁺][OH^-] = 1x10^-14

[H₃O⁺][1.51x10^-7] = 1x10^-14

[H₃O⁺] = 1x10^-14 / 1.51x10^-7

[H₃O⁺] = 6.62x10^-8 M (basic because it is less than 1x10^-7 M)

Solution B: [H₃O⁺] = 9.55×10⁻⁹ M

Follow the procedure outlined in A above and solve for [OH^-]

Answer should be [OH^-] = 1.05x10^-6 M (basic because it is greater than 1x10^-7 M)

Solution C: [H₃O⁺] = 7.07×10⁻⁴ M

Follow the procedure outlined in A above and solve for [OH^-]

Answer should be [OH^-] = 1.41x10^-11 M (acidic because it is less than 1x10^-7 M)