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Chemistry Grade 12 Unit 1: ACID-BASE EQUILIBRIA

69 national exam questions have come from this unit. It runs 55 pages; one careful study pass takes about 5.8 hours, and its difficulty is harder among Chemistry units. Each section below lists the questions set from it, with the year, and opens the page that teaches it.

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1.1 Acid-Base Concepts · read p. 1
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1.1.1 Arrhenius Concept of Acids and Bases · read p. 3
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1.1.2 Brønsted-Lowry Concept of Acids and Bases · read p. 5
  • 2018 E.C., Q44 – Which of the following is the major limitation of the Arrhenius concept of acids and bases?
  • 2017 E.C., Q17 – Which of the following compound is a Bronsted-Lowry base?
  • 2016 E.C., Q72 – Which of the following CORRECTLY describes conjugate acids and conjugate bases?
  • 2014 E.C., Q15 – For the reaction shown below, which of the following is a conjugate acid-base pair? HC 3 O -(aq) + H 2 O(l) ⇌ H 3 O + + CO 3 2-
  • 2013 E.C., Q30 – One of the following pairs shows Brønsted-Lowry acids behavior in water?
  • 2013 E.C., Q28 – An acid is a substance that
  • 2011 E.C., Q12 – Which of the following can function as both a Brønsted-Lowry acid and Brønsted-Lowry base?
  • 2011 E.C., Q69 – Consider the following equilibria: (I) (II) (III) In which of the equilibrium ( equilibria) does water act as a Brønsted-Lowry base?
  • 2010 E.C., Q10 – Which of the following is NOT both a Bronsted-Lowry acid and a Bronsted-Lowry base?
  • 2009 E.C., Q38 – Which of the following is the conjugate acid of the ion? H S 2 − S 2 −
  • 2008 E.C., Q17 – Which of the following combinations cannot produce a buffer solution?
  • 2007 E.C., Q9 – According to the Arrhenius concept, an acid is a substance that
  • 2007 E.C., Q14 – For the acid-base equilibrium. $\mathrm{HCO_3^- + H_2O \rightleftharpoons H_2CO_3 + OH^-}$ The Bronsted- Lowry acids are
  • 2006 E.C., Q1 – Which of the following is NOT a conjugate acid-base pair?
  • 2005 E.C., Q37 – Given the reaction: $\mathrm{H_2PO_4^- + H_2O \rightarrow H_3O^+ + HPO_4^{2-}}$ Which of the following represents a conjugate acid base pair?
  • 2005 E.C., Q10 – Which one of the mixture of the following pairs will NOT give a buffer solution?
1.1.3 Lewis Concept of Acids and Bases · read p. 11
1.2 Ionic Equlibria of Week Acids and Bases · read p. 14
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1.2.1 Ionization of Water · read p. 15
  • 2017 E.C., Q39 – Solutions can be classified based upon their pH values. What is a solution whose pH value is 13?
  • 2015 E.C., Q49 – The negative logarithm of the molar concentration of hydrogen ion to the base ten is known as ____________.
  • 2013 E.C., Q49 – Which one of the following is correct about K w at different temperature? The ionic product of water K w equals K w =1.0x10 -14 at 25 °C K w =2.92x10 -14 at 40 °C √K w =1x10 -7 √K w =1x10 -7
  • 2010 E.C., Q43 – What species of ions are present in a 0.1M solution of HCl and what will be their equilibrium concentrations? [H O] = 3 + 0.1M [OH] = − 10 M −13 [Cl] = − [H O] = 3 + 0.1M [OH] = − 0.1M [Cl] = − 0.1M
  • 2006 E.C., Q13 – A solution with a PH of 7.5 would be described as:
  • 2005 E.C., Q51 – Which of the following bio molecules forms a zwitterions at higher or lower PH?
1.2.2 Measures of the Strength of acids and Bases in Aqueous Solution · read p. 22
  • 2018 E.C., Q45 – A grade 12 student prepares 0.20 M aqueous solution of Acetic acid in the laboratory, according to the ionization equation given: CH₃COOH(aq) ⇌ H⁺(aq) + CH₃COO⁻(aq): Ka = 1.8 × 10⁻⁵. Which of the following is the closest
  • 2017 E.C., Q44 – Given the following information: CH₃COOH (aq) ⇌ CH₃COO⁻ (aq) + H⁺ (aq) CH₃COOH CH₃COO⁻ H⁺ Initial concentration (mol/L) 0.2 0 0 Change -X +X +X Equilibrium concentration 0.2 - X X X Which of the following expressions rep
  • 2017 E.C., Q35 – A 0.47 M aqueous solution of a weak base has a pOH of 2. What is $K_b$ for the weak base?
  • 2017 E.C., Q33 – For the dissociation of $\mathrm{HNO_2}$: $\mathrm{HNO_2(aq)} \rightleftharpoons \mathrm{NO_2^-(aq)} + \mathrm{H^+(aq)}$ What is the percent ionization of a 0.5 M solution of $\mathrm{HNO_2}$? ($K_a$ of $\mathrm{HNO_2}$
  • 2013 E.C., Q69 – Water is a weak electrolyte because
  • 2012 E.C., Q4 – How many moles of unknown weak acid (HA) in a 100 L solution are required to produce a solution with pH = 2? Ka of the unknown weak acid (HA) = 5×10^-3.
  • 2011 E.C., Q52 – If a solution of acetic acid (CH₃COOH) has a pH of 3.00, what is its concentration? Ka of acetic acid =
  • 2010 E.C., Q42 – A 0.2M solution of a weak acid HA is 1% ionized at $25^\circ\mathrm{C}$ $K_a$ for the acid is equal to:
  • 2009 E.C., Q26 – The initial rate of a reaction products was measured for several different starting concentrations of A and B, with the following results. Exp [A] [B] Initial rate of formation of C (M/s) 9.6 × 10−6 1 0.04 0.04 1.92 × 10
  • 2009 E.C., Q35 – Nitrous acid, $\mathrm{HNO_2}$ is 0.37% ionized in 3.0M solution. What is the $K_a$ for this acid?
  • 2008 E.C., Q19 – What is the ionization constant for a weak acid, $\mathrm{Ha}$, that is $1.60\%$ ionized in $0.0950\,\text{M}$ solution?
  • 2008 E.C., Q59 – A 1.0M solution a weak acid is found to dissociate by only 1.37%. Which of the following acid is it likely to be?
  • 2008 E.C., Q61 – A M solution has a PH of 10.00. The solution is a
  • 2006 E.C., Q66 – Which of the following statements is true about the percent ionization of a weak acid?
1.3 Common Ion Effect and Buffer Solution · read p. 31
Not asked in a national paper yet.
1.3.1 The Common Ion Effect · read p. 32
  • 2016 E.C., Q20 – The shift in the position of equilibrium caused by the addition of an ion already involved in the reaction is known as _________.
1.3.2 Buffer Solutions · read p. 34
  • 2018 E.C., Q46 – Consider a solution that is 0.10 M acetic acid (CH₃COOH) and 0.20 M sodium acetate (NaCH₃COO). Which of the following statements is correct?
  • 2018 E.C., Q47 – Which of the following procedures can NOT produce a buffer solution?
  • 2018 E.C., Q48 – A buffer solution is prepared using Acetic acid (CH₃COOH) and its conjugate base Sodium acetate (CH₃COONa). Under which condition will this buffer solution have maximum buffering capacity?
  • 2014 E.C., Q47 – What is the effect of a common ion in an electrolytic solution?
  • 2013 E.C., Q27 – The reaction between a weak acid and strong base as represented by the reaction between acetic acid and NaOH gives a basic solution because
  • 2013 E.C., Q26 – One of the following given pairs represents examples of buffer systems
  • 2012 E.C., Q8 – Addition of HCl to an aqueous buffer solution containing NH3 and NH4Cl cause which of the following to occur? I. pH of the solution increase II. pH of the solution decrease III. NH4+ concentration increase IV. NH3 concen
  • 2011 E.C., Q29 – What is the pH of a 0.10 M solution of NH₃, a weak base, whose ?
  • 2011 E.C., Q40 – A chemist creates a buffer solution by mixing equal volumes of a 0.2-molar HOCl solution and a 0.2-molar KOCl solution. Which of the following will occur when a small amount of KOH is added to the solution? I. The concen
  • 2009 E.C., Q34 – The suppression of ionization of a weak acid or a weak base by adding one of its own ions is known as:
  • 2007 E.C., Q71 – The following bases and their conjugate acids (as the chlorides) are available in the laboratory: ( ), C H NCH CH NH 6 5 3 2 2 K = b 6.4 × 10−4 CH NH 3 2 K = b 4.4 × 10−4 ( ) and ( ). Which of these acid-base pairs are t
  • 2007 E.C., Q29 – The acid-base indicator bromocresol green is a weak acid. The yellow acid and blue base forms of the indicator are present in equal concentrations in a solution when the PH is 4.68. What is the PKa of bromocresol green?
  • 2007 E.C., Q56 – The of a weak monoprotic acid is 4.8. What should be the ratio of [Acid]/[Salt] of a buffer, if PH = 5.8 is required?
  • 2005 E.C., Q66 – To $0.2\,\mathrm{M}$ solution of a weak monoprotic acid, $\mathrm{HA}$, enough quantity of its sodium salt, $\mathrm{NaA}$, was dissolved to give a concentration of $0.2\,\mathrm{M}$ of the salt. What will be the acid co
1.4 Hydrolysis of Salts · read p. 39
Not asked in a national paper yet.
1.4.1 Hydrolysis of Salts of Strong Acids and Strong Bases · read p. 39
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1.4.2 Hydrolysis of Salts of Weak Acids and Strong Bases · read p. 40
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1.4.3 Hydrolysis of Salts of Strong Acids and Weak Bases · read p. 40
  • 2018 E.C., Q49 – Which of the following salts will produce an acidic solution when dissolved in water?
  • 2013 E.C., Q48 – In the reaction mixture of two species NH 4 OH and NH 4 Cl, which one of the following is true about the reaction mixture?
  • 2012 E.C., Q6 – Which of the following 0.1 M solutions has the lowest pH?
  • 2012 E.C., Q22 – Which of the following salts would form an acidic solution? I. KCl II. NaF III. NH4Cl IV. CaCO3
1.4.4 Hydrolysis of Salts of Weak Acids and Week Bases · read p. 41
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1.5 Acid–Base Indicators and Titrations · read p. 43
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1.5.1 Acid–Base Indicators · read p. 43
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1.5.2 Equivalents of Acids and Bases · read p. 44
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1.5.3 Acid–Base Titrations · read p. 45
  • 2017 E.C., Q30 – Which statement distinguishes equilibrium point from end point in acid-base titration?
  • 2016 E.C., Q21 – Which of the following is CORRECT about equivalents of acids and bases?
  • 2015 E.C., Q24 – The point in a titration at which the number of moles of OH ions added to a solution is equal to the number of + moles of H ions originally present is
  • 2014 E.C., Q40 – Which of the following statements is true for an acid-base titration?
  • 2012 E.C., Q9 – What is the equivalence point pH of the solution formed by the titration of 50 mL of 0.15 M CH3COOH using 25 mL of 0.3 M NaOH? [Use log 7.5 = 0.87, Kb of acetate ion = 5.6×10^{-10}]
  • 2007 E.C., Q48 – The following data were collected at the end point of a titration performed to find the molarity of an HCl solution. Volume of acid (HCl) used = 14.4ml Volume of base (NaOH) used = 22.4ml Molarity of standard base (NaOH)
  • 2006 E.C., Q12 – During the titration of a known volume of a strong acid with a strong base, there is