ACIDS AND BASES QUIZ Click to start

Question 1 Which one of the followig descriptions defines a strong acid? It is concentrated. It does dissociate in water. It absorbs water from the air. It almost completely dissociate in water.

Wrong Answer! A strong acid is almost completely dissociated. HA(aq)  H + (aq) + A - (aq)

Zn + 2H 2 SO 4  2ZnS + 2H 2 O + 3O 2 Question 2 Which of the following represents the reaction between zinc powder and a dilute aqueuous solution of sulfuric acid? Zn + H 2 SO 4  ZnSO 4 + H 2 4Zn + H 2 SO 4  4ZnO + H 2 S Zn + H 2 SO 4  ZnH 2 + SO 2 + O 2

Wrong Answer! Metals react with acids to form hydrogen and salt.

Question 3 When the following 1.0 moldm -3 solutions are listed in increasing order of pH (lowest first), what is the correct order ? HNO 3 <H 2 CO 3 <Ba(OH) 2 <NH 3 NH 3 <Ba(OH) 2 <H 2 CO 3 HNO 3 HNO 3 <H 2 CO 3 <NH 3 <Ba(OH) 2 Ba(OH) 2 <H 2 CO 3 <NH 3 <HNO 3

Wrong Answer! strong acid < weak acid < weak base < strong base

Question 4 The amino acid alanine has the structure: H 2 N-CH(CH 3 )-COOH Which of the following species represents its conjugate acid ? NH 2 CH(CH 3 )COO - + NH 3 CH(CH 3 )COO - + NH3CH(CH 3 )COOH NH 3 CH(CH 3 )COOH

Wrong Answer! The conjugate acid is formed by protonation of the amino group

Question 5 In the equilibrium below, which species represents a conjugate acid-base pair? CH 2 ClCOOH(aq) + H 2 O(l) CH 2 ClCOO - (aq) + H 3 O + (aq) H 2 O/H 3 O + CH 2 ClCOO - /H 3 O + CH 2 ClCOOH/H 2 O H 2 O/CH 2 ClCOO -

Wrong Answer! A conjugate acid-base pair differ by a proton (H + )

Question 6 Hydrogen chloride dissolved in water reacts with magnesium. Hydrogen chloride dissolved in ethanol does not react with magnesium. Which statement accounts for this observation? Hydrogen chloride does not form ions in water. Ethanol accepts hydrogen ions (protons) and water does not. Water is a hydrogen ion/proton acceptor Magnesium is very soluble in ethanol but insoluble in water.

Wrong Answer! Acid behaviour is observed in water since the water molecule is a strong base (proton acceptor) and forms hydronium ions, H 3 O +.

Question 7 A dilute aqueous solution of benzenecarboxylic acid (an organic acid) is a poor conductor of electricity. Which of the following statements accounts for this observation? Benzenecarboxylic acid solution has a high concentration of ions. Benzenecarboxylic acid is only slightly dissociated in water. It is a strong acid. Benzenecarboxylic acid is completely dissociated in water.

Wrong Answer! The low concentration of ions accounts for its low conductivity.

Question 8 A decrease in the pH of an aqueous solution corresponds to: A decrease in the H + concentration and an increase in the OH - concentration. An increase in the OH - concentration and an increase in the H + concentration. A decrease in the H + concentration with no change in the OH - concentration. An increase in the H + concentration and a decrease in the OH - concentration.

Wrong Answer! A decrease in pH correlates to an increase in the hydrogen ion concentration.

Question 9 Calcium oxide is added to a lake to neutralise the effects of acid rain. The pH value of the lake water rises from 4 to 6. What is the change in concentration of [H+(aq)] in the lake water? An increase by a factor of 2. An increase by a factor of 100. A decrease by a factor of 100. A decrease by a factor of 2.

Wrong Answer! pH and [H + ] are inversely related. An increase in the pH by a value of 1 corresponds to x10 decrease in the H +

Question 10 Which of the ions behave as a Br Ø nsted – Lowry base and as a Br Ø nsted – Lowry acid? CO 3 2- HSO 4 - Such a species does not exist. NO 3 -

Wrong Answer! HSO 4 -  SO H + HSO H +  H 2 SO 4

Question 11 The pH of solution X is 1 and that of Y is 2. Which statement is correct about the hydrogen ion concentrations in the two solutions? [ H + ] in X is half that in Y. [H + ] in X is twice that in Y. [H + ] in X is a hundred times that in Y. [H + ] in X is ten times that in Y.

Wrong Answer! A change in pH of 1 unit corresponds to a change of x10 in the concentration of hydrogen ions.

HNO 3 + H 2 O  H 3 O + + NO 3 - Question 12 In which of the following reactions does the nitric acid molecule act as a base? HNO 3 + 2H 2 SO 4  NO HSO H 3 O + HNO 3  H + + NO 3 - HNO 3 + CH 3 COOH  CH 3 COOH NO 3 -

Wrong Answer! The sulfuric acid molecule is deprotonated.

Question 13 Which of the following would exactly neutralise 100cm 3 of 1 mol dm -3 sulfuric acid? 0.2 mol Na 2 CO mol NH mol KOH 0.1 mol Ba(OH) 2

Wrong Answer! H 2 SO 4 + Ba(OH) 2  BaSO 4 + 2H 2 O 0.1 mol of sulfuric acid reacts with 0.1 mol of barium hydroxide.

Question 14 Which is not a strong acid? Carbonic acid Nitric acid Hydrochloric acid Sulfuric acid

Wrong Answer! Carbonic acid is a weak acid

Question 15 Which equation correctly describes phosphoric(V) acid behaving as a monoprotic acid in aqueous solution? H 3 PO 4 (aq)  2H + (aq)+ HPO 4 2- (aq) H 3 PO 4 (aq)  3H + (aq)+ PO 4 3- (aq) H 3 PO 4 (aq)  H + (aq)+ H 2 PO 4 - (aq) H 2 PO 4 (aq)  H + (aq)+ HPO 4 2- (aq)

Wrong Answer! A monoprotic acid releases 1 hydrogen ion per molecule in water.

Question 16 Ammonia molecules in aqueous solution can be considered as: A Lewis acid (only) A Lewis base (only) Both a Br Ø nsted – Lowry base and a Lewis base A Br Ø nsted – Lowry base (only)

Wrong Answer! The ammonia molecule has an available lone pair of electrons and is able to accept a hydrogen ion and form the ammonium ion (via a dative bond form).

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