Problem 15
What is meant by pH? True or false: A strong acid solution always has a lower pH than a weak acid solution. Explain.
Problem 16
Why is the pH of water at \(25^{\circ} \mathrm{C}\) equal to 7.00\(?\)
Problem 17
Can the pH of a solution be negative? Explain.
Problem 18
Is the conjugate base of a weak acid a strong base? Explain. Explain why \(\mathrm{Cl}^{-}\) does not affect the pH of an aqueous solution.
Problem 20
The salt \(\mathrm{BX}\) , when dissolved in water, produces an acidic solution. Which of the following could be true? (There may be more than one correct answer.) a. The acid HX is a weak acid. b. The acid HX is a strong acid. c. The cation \(B^{+}\) is a weak acid. Explain.
Problem 21
Anions containing hydrogen (for example, \(\mathrm{HCO}_{3}^{-}\) and \(\mathrm{H}_{2} \mathrm{PO}_{4}^{-} )\) usually show amphoteric behavior. Write equations illustrating the amphoterism of these two anions.
Problem 22
Which of the following conditions indicate an acidic solution at \(25^{\circ} \mathrm{C} ?\) a. \(\mathrm{pH}=3.04\) b. \(\left[\mathrm{H}^{+}\right]>1.0 \times 10^{-7} \mathrm{M}\) c. \(\mathrm{pOH}=4.51\) d. \(\left[\mathrm{OH}^{-}\right]=3.21 \times 10^{-12} \mathrm{M}\)
Problem 23
Which of the following conditions indicate a basic solution at \(25^{\circ} \mathrm{C} ?\) a. \(\mathrm{pOH}=11.21\) b. \(\mathrm{pH}=9.42\) c. \(\left[\mathrm{OH}^{-}\right]>\left[\mathrm{H}^{+}\right]\) d. \(\left[\mathrm{OH}^{-}\right]>1.0 \times 10^{-7} \mathrm{M}\)
Problem 24
What is the \(\mathrm{p} K_{\mathrm{a}}\) of an acid? As the \(\mathrm{p} K_{\mathrm{a}}\) value increases, does acid strength increase or decrease? Explain.
Problem 25
How many significant figures are there in the following num- bers: \(10.78,6.78,0.78 ?\) If these were pH values, to how many significant figures can you express the \(\left[\mathrm{H}^{+}\right] ?\) Explain any discrepancies between your answers to the two questions.
