The pH scale and pH calculations

Answer Key - Grade 10 Science Worksheet - Challenge Me

Circle the best answer, or write your answer on the line.

1. 1.

   In 0.10 M acetic acid, [H⁺] = 0.0013 M. Using pH = −log[H⁺], what is the pH to two decimal places, Ari?

   2.89
2. 2.

   In 0.010 M acetic acid, [H⁺] = 0.00042 M. Using pH = −log[H⁺], what is the pH to two decimal places, Bo?

   3.38
3. 3.

   In 1.0 M acetic acid, [H⁺] = 0.0042 M. Using pH = −log[H⁺], what is the pH to two decimal places, Esme?

   2.38
4. 4.

   A solution has pH 3.0. What is its [H⁺], Jun?

   • 0.003 M
   • 3 M
   • 0.001 M
5. 5.

   0.10 M HCl has pH 1.0 but 0.10 M acetic acid has pH 2.89. Why, Luz?

   • Acetic acid ionizes partly
   • The HCl solution is more dilute
   • Acetic acid has more H⁺
6. 6.

   Milo says pH 2 is twice as acidic as pH 4 because 4 is double 2. Agree or disagree?

   • Disagree: it has 100 times more H⁺
   • Agree: 4 is exactly twice as big as 2
   • Agree: lower pH is less acidic
7. 7.

   Noah says going from pH 7 to pH 4 makes [H⁺] three times bigger. Agree or disagree?

   • Disagree: it is 1,000 times bigger
   • Agree: [H⁺] falls as pH falls
   • Agree: the pH fell by exactly three
8. 8.

   Pia says a basic solution has no H⁺ ions at all. Agree or disagree?

   • Disagree: it has fewer H⁺ than OH⁻
   • Agree: H⁺ ions belong to acids alone
   • Agree: bases contain no hydrogen
9. 9.

   1.0 M NaOH has pH 14.0 at 25 °C. What is its pOH, Tala?

   • 14.0
   • 7.0
   • 0.0
10. 10.

    Pure water at 25 °C has equal [H⁺] and [OH⁻]. What is each, Zee?

    • 1 × 10⁻¹⁴ M
    • 7 M
    • 1 × 10⁻⁷ M