pH and pK - AP Chemistry

1. Calculate $K_b$ if $K_a = 1.0 \times 10^{-5}$ for a conjugate acid-base pair.

   $K_b = 1.0 \times 10^{-9}$. Using $K_a \times K_b = 1.0 \times 10^{-14}$.

2. Calculate the pH of a 0.05 M H$_2$SO$_4$ solution.

   pH ≈ 1. H$_2$SO$_4$ is diprotic; [H$^+$] = 0.10 M.

3. Identify the pH range of a basic solution.

   pH > 7. Higher OH$^-$ concentration than neutral solution.

4. What is the pK$_b$ of a strong base?

   Low pK$_b$. Strong bases have very negative pK$_b$ values.

5. Identify the pH range of an acidic solution.

   pH < 7. Higher H$^+$ concentration than neutral solution.

6. What is the formula for the base dissociation constant ($K_b$)?

   $K_b$ is the equilibrium constant for the dissociation of a base. Measures the extent of base ionization in solution.

7. Calculate the pH of a 0.1 M HCl solution.

   pH = 1. HCl completely ionizes; [H$^+$] = 0.1 M.

8. Find the pOH of a solution with pH = 2.

   pOH = 12. Using the relationship pH + pOH = 14.

9. What does a high pK$_a$ indicate about the strength of an acid?

   Weak acid. High pK$_a$ means low ionization tendency.

10. Calculate the [H$^+$] for a solution with pH = 6.

    [H$^+$] = $1.0 \times 10^{-6}$ M. Using [H$^+$] = $10^{-\text{pH}}$ relationship.

11. What is the relationship between $K_a$ and $pK_a$?

    $\text{pK}_a = -\text{log}_{10}(K_a)$. Takes the negative logarithm of the acid constant.

12. What is the relationship between $K_a$ and $K_b$ for a conjugate acid-base pair?

    $K_a \times K_b = K_w$. Fundamental relationship for conjugate pairs.

13. Calculate the [OH$^-$] for a solution with pOH = 8.

    [OH$^-$] = $1.0 \times 10^{-8}$ M. Using [OH$^-$] = $10^{-\text{pOH}}$ relationship.

14. What is the pH of a 0.1 M acetic acid solution with $K_a = 1.8 \times 10^{-5}$?

    pH ≈ 2.88. Using the weak acid approximation formula.

15. State the relationship between pH and pOH in water at 25°C.

    $\text{pH} + \text{pOH} = 14$. Based on the ion product of water at 25°C.

16. Identify the term for the negative logarithm of the base dissociation constant.

    pK$_b$. Standard notation for base dissociation constant.

17. What is the pH of pure water at 25°C?

    pH = 7. Autoionization gives equal H$^+$ and OH$^-$.

18. Define the term 'acid dissociation constant' ($K_a$).

    $K_a$ is the equilibrium constant for the dissociation of an acid. Measures the extent of acid ionization in solution.

19. What is the formula for calculating pH?

    $\text{pH} = -\text{log}_{10}[\text{H}^+]$. Negative log base 10 of hydrogen ion concentration.

20. Which has a higher pH: 0.1 M HCl or 0.1 M CH$_3$COOH?

    0.1 M CH$_3$COOH. Acetic acid is weak, HCl is strong acid.

21. Calculate the pH of a 0.001 M HNO$_3$ solution.

    pH = 3. HNO$_3$ completely ionizes; [H$^+$] = 0.001 M.

22. Determine the pH of a 0.01 M NaOH solution.

    pH = 12. NaOH gives [OH$^-$] = 0.01 M, so pOH = 2.

23. Calculate the pK$_a$ for an acid with $K_a = 3.2 \times 10^{-4}$.

    pK$_a$ ≈ 3.5. Using $\text{pK}_a = -\log(3.2 \times 10^{-4})$.

24. What is the pH of a 1.0 M solution of a strong base?

    pH = 14. Strong base gives [OH$^-$] = 1.0 M, pOH = 0.

25. Find the pH of a 0.1 M solution of a strong acid.

    pH = 1. Strong acids completely ionize in solution.

26. If $K_a$ is small, is the acid strong or weak?

    Weak acid. Small $K_a$ means limited ionization.

27. If $K_a$ is large, is the acid strong or weak?

    Strong acid. Large $K_a$ means extensive ionization.

28. What is the formula for calculating pOH?

    $\text{pOH} = -\text{log}_{10}[\text{OH}^-]$. Negative log base 10 of hydroxide ion concentration.

29. Calculate the pK$_b$ for a base with $K_b = 4.5 \times 10^{-8}$.

    pK$_b$ ≈ 7.35. Using $\text{pK}_b = -\log(4.5 \times 10^{-8})$.

30. What is the pH of a 0.01 M NH$_3$ solution ($K_b = 1.8 \times 10^{-5}$)?

    pH ≈ 11.13. Using weak base approximation with given $K_b$.

31. State the relationship between $K_b$ and $pK_b$.

    $pK_b = -\log_{10}(K_b)$. Takes the negative logarithm of the base constant.

32. What is the pH of a neutral solution at 25°C?

    pH = 7. Equal concentrations of H$^+$ and OH$^-$ ions.

33. What is the formula for the ion product of water ($K_w$) at 25°C?

    $K_w = 1.0 \times 10^{-14}$. Ion product constant for water at standard temperature.

34. Calculate the pH of a solution with [H$^+$] = $1.0 \times 10^{-3}$ M.

    pH = 3. Using $\text{pH} = -\log(1.0 \times 10^{-3}) = 3$.

35. What does a low pK$_b$ indicate about the strength of a base?

    Strong base. Low pK$_b$ means high ionization tendency.

36. Determine the pOH of a solution with [OH$^-$] = $1.0 \times 10^{-4}$ M.

    pOH = 4. Using $\text{pOH} = -\log(1.0 \times 10^{-4}) = 4$.

37. Find the pH of a solution with pOH = 5.

    pH = 9. Using the relationship pH + pOH = 14.

38. If pK$_a$ is 4, what is the strength of the acid?

    Weak acid. pK$_a$ = 4 indicates moderate acid strength.

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