Acid-Base Theory
What is the definition of a Bronsted-Lowry Acid?
A substance that donates a proton (H+).
Which acid is stronger: HCl (Ka ≈ 10^7) or HF (Ka = 7.2 x 10^-4)?
HCl is stronger because it has a much larger Ka value.
What is the pH of a 0.10 M HCl solution?
pH = 1
Name the acid with the formula HCl.
Hydrochloric acid.
What is the color of litmus paper in a neutral solution?
Purple.
In the reaction: 𝑁𝐻3+𝐻2𝑂↔𝑁𝐻4+𝑂𝐻−, identify the conjugate acid-base pairs.
𝑁𝐻3 And 𝑁𝐻4+ (conjugate acid-base pair), 𝐻2𝑂 and 𝑂𝐻− (conjugate acid-base pair).
What does the pKa value indicate about an acid's strength?
A lower pKa value indicates a stronger acid, as it signifies a higher Ka and greater dissociation in water.
DAILY DOUBLE
Calculate the pH of a 0.10 M NaOH solution
pH = 13
Name the acid with the formula H2SO4.
Sulfuric acid.
What is the endpoint in a titration?
The point at which the indicator changes color, signaling that the reaction is complete.
Explain why water is considered amphoteric.
Water can act as both an acid and a base; it can donate a proton to become 𝑂𝐻− or accept a proton to become 𝐻3𝑂+.
Determine the relative strength of acetic acid (Ka = 1.8 x 10^-5) compared to formic acid (Ka = 1.8 x 10^-4).
Formic acid is stronger than acetic acid because it has a higher Ka value.
If the pH of a solution is 4, what is the concentration of H+ ions?
[H+] = 1 x 10^-4 M.
Name the acid with the formula HClO.
Hypochlorous acid.
How does a buffer solution work?
A buffer resists changes in pH by neutralizing added acids or bases through its conjugate acid-base pair.
Compare the strength of chlorous acid (Ka = 1.1 x 10^-2) and hypochlorous acid (Ka = 3.0 x 10^-8). What does it indicate about the acid?
Chlorous acid is stronger than hypochlorous acid because it has a larger Ka value, indicating a greater degree of dissociation in water.
Explain the relationship between the strength of an acid and its conjugate base.
The stronger the acid, the weaker its conjugate base; this is because a strong acid dissociates completely, leaving behind a very weak conjugate base.
Calculate the pH of a 0.05 M HClO4 solution. Round to the tenths place.
pH ≈ 1.3
Name the base with the formula KOH.
Potassium hydroxide.
Calculate the pH of a solution containing 0.40 M CH3COOH and 0.20 M CH3COONa (Ka = 1.8 x 10^-5). (using Henderson-Hasselbalch equation) Round to the hundredths place.
pH ≈ 4.57
Explain the concept of a polyprotic acid using sulfuric acid as an example. Hint: Use strength.
A polyprotic acid can donate more than one proton. Sulfuric acid (H2SO4) donates its first proton completely (strong acid) and the second proton partially (weak acid).
Calculate the pH of a 0.25 M NH3 solution with Kb = 1.8 x 10^-5. Round to the hundredths place.
pH ≈ 11.63
What is the pH of a buffer solution containing 0.5 M CH3COOH and 0.5 M CH3COONa (Ka for CH3COOH = 1.77 x 10^-5)? (using Henderson-Hasselbalch equation)
pH ≈ 4.74.
Provide the name and molecular mass for H3PO4.
Phosphoric acid. Polyprotic acids are named similarly to monoprotic acids but can donate more than one proton. Molecular mass = 97.994
DAILY DOUBLE
Predict the pH of a solution when ammonium chloride (NH4Cl) is dissolved in water. Explain the process and provide a step-by-step example calculation. Round answer to the hundredths place.
Explanation: Ammonium chloride (NH4Cl) is a salt formed from a weak base (NH3) and a strong acid (HCl). In water, NH4Cl dissociates into NH4+ and Cl-. NH4+ (ammonium ion) acts as a weak acid, releasing H+ ions, while Cl- is the conjugate base of a strong acid and does not affect the pH.
Thus, the pH of a 0.1 M NH4Cl solution is approximately 5.13.