Question

SHOW ALL YOUR WORK!!

Answer 1

Answer:

1. [H₃O⁺] = 2.0 x 10⁻⁹ M.

   [OH⁻] = 3.55 x 10⁻⁶ M.

  The solution is basic.

2. [H₃O⁺] = 3.16 x 10⁻⁴ M.

   [OH⁻] = 3.16 x 10⁻¹¹  M.

  The solution is acidic.

3. [OH⁻] = 2.72 x 10⁻⁷ M.

   pH = 7.435.

   The solution is basic.

4. [OH⁻] = 9.89 x 10⁻³ M.

   pH = 2.0.

   The solution is acidic.

5. [H₃O⁺] = 1.82 x 10⁻⁵ M.

   pH = 4.74.

  The solution is acidic.

6.

[H₃O⁺] = 1.176 x 10⁻¹³ M.

   pH = 12.93.

   The solution is basic.

7. The solution is basic.

8. The solution is acidic.

9. The solution is acidic.

10. The solution is neutral.

Explanation:

• We can use the following relations:

pH = - log[H⁺],

pOH = - log[OH⁻],

Kw = [H⁺][OH⁻] = 10⁻¹⁴.

• To determine whither the solution is acidic, basic or neutral:

pH scale is a scale from 0 to 14, from which we can determine the nature of the solution:

• If the (0 ≤ pH > 7), the solution is acidic.

• If the pH = 7, the solution is neutral.

• If the (7 < pH ≥ 14), the solution is basic.

1. Given pH = 8.55, Find: [H₃O⁺] and [OH⁻], Is this acidic, basic or neutral?

∵ pH = - log[H₃O⁺]

∴ 8.55 =  - log[H₃O⁺]

∴ [H₃O⁺] = 2.0 x 10⁻⁹ M.

∵ Kw = [H₃O⁺][OH⁻] = 10⁻¹⁴.

∴  [OH⁻] = 10⁻¹⁴/[H₃O⁺] = 10⁻¹⁴/(2.0 x 10⁻⁹ M) = 3.55 x 10⁻⁶ M.

∵ pH = 8.55 > 7,

∴ The solution is basic.

2. Given pH = 3.50, Find: [H₃O⁺] and [OH⁻], Is this acidic, basic or neutral?

∵ pH = - log[H₃O⁺]

∴ 3.50 =  - log[H₃O⁺]

∴ [H₃O⁺] = 3.16 x 10⁻⁴ M.

∵ Kw = [H₃O⁺][OH⁻] = 10⁻¹⁴.

∴  [OH⁻] = 10⁻¹⁴/[H₃O⁺] = 10⁻¹⁴/(3.16 x 10⁻¹⁴ M) = 3.16 x 10⁻¹¹ M.

∵ pH = 3.50 < 7,

∴ The solution is acidic.

3. Given [H₃O⁺] = 3.67 x 10⁻⁸ M, Find: [OH⁻] and pH, Is this acidic, basic or neutral?

∵ Kw = [H₃O⁺][OH⁻] = 10⁻¹⁴.

∴  [OH⁻] = 10⁻¹⁴/[H₃O⁺] = 10⁻¹⁴/(3.67 x 10⁻⁸ M) = 2.72 x 10⁻⁷ M.

∵ pH = - log[H₃O⁺]

∴ pH = - log(3.67 x 10⁻⁸ M) = 7.435.

∵ pH = 7.435 > 7,

∴ The solution is basic.

4. Given [H₃O⁺] = 9.89 x 10⁻³ M, Find: [OH⁻] and pH, Is this acidic, basic or neutral?

∵ Kw = [H₃O⁺][OH⁻] = 10⁻¹⁴.

∴  [OH⁻] = 10⁻¹⁴/[H₃O⁺] = 10⁻¹⁴/(9.89 x 10⁻³ M) = 9.89 x 10⁻³ M.

∵ pH = - log[H₃O⁺]

∴ pH = - log(9.89 x 10⁻³ M) = 2.0.

∵ pH = 2.0 < 7,

∴ The solution is acidic.

5. Given [OH⁻] = 5.5 x 10⁻¹⁰ M, Find: [H₃O⁺] and pH, Is this acidic, basic or neutral?

 ∵ Kw = [H₃O⁺][OH⁻] = 10⁻¹⁴.

∴  [H₃O⁺] = 10⁻¹⁴/[OH⁻] = 10⁻¹⁴/(5.5 x 10⁻¹⁰ M) = 1.82 x 10⁻⁵ M.

∵ pH = - log[H₃O⁺]

∴ pH = - log(1.82 x 10⁻⁵ M) = 4.74.

∵ pH = 4.74 < 7,

∴ The solution is acidic.

6. Given [OH⁻] = 8.5 x 10⁻² M, Find: [H₃O⁺] and pH, Is this acidic, basic or neutral?

∵ Kw = [H₃O⁺][OH⁻] = 10⁻¹⁴.

∴  [H₃O⁺] = 10⁻¹⁴/[OH⁻] = 10⁻¹⁴/(8.5 x 10⁻² M) = 1.176 x 10⁻¹³ M.

∵ pH = - log[H₃O⁺]

∴ pH = - log(1.176 x 10⁻¹³ M) = 12.93.

∵ pH = 12.93 > 7,

∴ The solution is basic.

7. Given [OH⁻] = 3.75 x 10⁻⁵ M, Is this acidic, basic or neutral?  How do you know?

∵ Kw = [H₃O⁺][OH⁻] = 10⁻¹⁴.

∴  [H₃O⁺] = 10⁻¹⁴/[OH⁻] = 10⁻¹⁴/(3.75 x 10⁻⁵ M) = 2.67 x 10⁻¹⁰ M.

∵ pH = - log[H₃O⁺]

∴ pH = - log(2.67 x 10⁻¹⁰ M) = 9.57.

∵ pH = 9.57 > 7,

∴ The solution is basic.

8. Given [H₃O⁺] = 3.75 x 10⁻³ M, Is this acidic, basic or neutral?  How do you know?

∵ pH = - log[H₃O⁺]

∴ pH = - log(3.75 x 10⁻³ M) = 2.43.

∵ pH = 2.43 < 7,

∴ The solution is acidic.

9. Given pH = 6.75,  Is this acidic, basic or neutral?  How do you know?

∵ pH = 6.75 < 7,

∴ The solution is acidic.

10. Given [H₃O⁺] = 1.00 x 10⁻⁷ M, Is this acidic, basic or neutral?  How do you know?

∵ pH = - log[H₃O⁺]

∴ pH = - log(1.0 x 10⁻⁷ M) = 7.0.

∵ pH = 7.0,

∴ The solution is neutral.