| Date | May 2017 | Marks available | 1 | Reference code | 17M.3.hl.TZ2.4 |
| Level | HL | Paper | 3 | Time zone | TZ2 |
| Command term | Identify | Question number | 4 | Adapted from | N/A |
Question
EDTA is produced by reacting ethane-1,2-diamine with chloroethanoic acid, ClCH2COOH.
Identify the other product formed.
Explain why EDTA, a chelating agent, is more effective in removing heavy metal ions from solution than monodentate ligands.
Markscheme
HCl/hydrogen chloride
Accept “hydrochloric acid”.
[1 mark]
forms four/six/several/multiple coordinate/coordination bonds «to a central metal ion»
OR
is a polydentate/tetradentate/hexadentate ligand
forms more stable complex/stronger bonds with central metal ion
OR
increases entropy/S by releasing smaller «monodentate ligand» molecules previously complexed
complex ions are much larger «and can be removed easily due to large size of chelate complexes»
OR
heavy metal ions trapped inside the ligand/become «biologically» inactive/nontoxic/harmless
Accept “dative «covalent»” for “coordinate/coordination”.
Do not accept just “chelates”.
[3 marks]
Examiners report
Syllabus sections
- 17N.2.hl.TZ0.1e: Suggest why the enthalpy change of neutralization of CH3COOH is less negative than that of HCl.
- 18M.1.sl.TZ2.20: Which statement is correct? A. A strong acid is a good proton donor and has a strong...
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18N.2.hl.TZ0.6a.i:
State the equation for the reaction of each substance with water.
- 22M.2.sl.TZ2.3c(ii): State the meaning of a strong Brønsted–Lowry acid.
- 16N.2.sl.TZ0.2a: Distinguish between a weak acid and a strong acid. Weak acid: Strong acid:
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17M.1.sl.TZ1.20:
Which 1.0 moldm–3 solution has the highest pH?
A. Ammonium chloride
B. Sulfuric acid
C. Sodium chloride
D. Ammonia
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22M.1.sl.TZ2.20:
What is the strongest acid in the equation below?
H3AsO4 + H2O H2AsO4− + H3O+ Kc = 4.5 × 10−4
A. H3AsO4
B. H2O
C. H2AsO4−
D. H3O+
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22M.1.sl.TZ2.30:
20 cm3 of 1 mol dm−3 sulfuric acid was added dropwise to 20 cm3 of 1 mol dm−3 barium hydroxide producing a precipitate of barium sulfate.
H2SO4 (aq) + Ba(OH)2 (aq) → 2H2O (l) + BaSO4 (s)
Which graph represents a plot of conductivity against volume of acid added?
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19N.2.sl.TZ0.4a(iii):
The dissociation of citric acid is an endothermic process. State the effect on the hydrogen ion concentration, [H+], and on the equilibrium constant, of increasing the temperature.
- 19N.2.sl.TZ0.4a(ii): The value of the equilibrium constant for the first dissociation at 298 K is 5.01 ×...
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18M.2.sl.TZ1.5a:
Predict, giving a reason, a difference between the reactions of the same concentrations of hydrochloric acid and ethanoic acid with samples of calcium carbonate.
-
18M.2.hl.TZ1.5a:
Predict, giving a reason, a difference between the reactions of the same concentrations of hydrochloric acid and ethanoic acid with samples of calcium carbonate.
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17M.2.hl.TZ2.8b.v:
State a technique other than a pH titration that can be used to detect the equivalence point.
- 22M.2.hl.TZ2.6d(ii): State the meaning of a strong Brønsted–Lowry acid.
-
18N.2.sl.TZ0.6a:
State the equation for the reaction of each substance with water.
-
18N.1.sl.TZ0.20:
What is the order of increasing pH for the following solutions of the same concentration?
A. HCl (aq) < NH3 (aq) < NaOH (aq) < CH3COOH (aq)
B. CH3COOH (aq) < HCl (aq) < NH3 (aq) < NaOH (aq)
C. HCl (aq) < CH3COOH (aq) < NH3 (aq) < NaOH (aq)
D. NaOH (aq) < NH3 (aq) < CH3COOH (aq) < HCl (aq)
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19M.2.hl.TZ1.5a:
Outline why ethanoic acid is classified as a weak acid.
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17M.2.sl.TZ1.4c:
Hydrazine reacts with water in a similar way to ammonia. Deduce an equation for the reaction of hydrazine with water.
- 19N.2.sl.TZ0.4b: Outline one laboratory methods of distinguishing between solutions of citric acid and...
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19M.2.sl.TZ2.5a(i):
Distinguish between a weak and strong acid.
Weak acid:
Strong acid:
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19N.3.sl.TZ0.16a:
Identify the compound responsible for the acidity of gastric juice, and state whether it is a strong or weak acid.
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19N.2.hl.TZ0.4a(iii):
The dissociation of citric acid is an endothermic process. State the effect on the hydrogen ion concentration, [H+], and on Ka, of increasing the temperature.
- 19N.2.hl.TZ0.4a(ii): The value of Ka at 298 K for the first dissociation is 5.01 × 10−4. State, giving a reason,...
- 19N.2.hl.TZ0.4b: Outline two laboratory methods of distinguishing between solutions of citric acid and...
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17M.2.sl.TZ1.4d:
Outline, using an ionic equation, what is observed when magnesium powder is added to a solution of ammonium chloride.
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19M.2.sl.TZ1.5a:
Outline why ethanoic acid is classified as a weak acid.
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18M.2.sl.TZ2.2b.ii:
State and explain the effect on the rate of reaction if ethanoic acid of the same concentration is used in place of hydrochloric acid.
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17M.3.sl.TZ2.14b.ii:
Describe how large amounts of CO2 could reduce the pH of the ocean using an equation to support your answer.
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19M.2.hl.TZ2.5a(i):
Distinguish between a weak and strong acid.
Weak acid:
Strong acid:
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21M.2.sl.TZ1.2b(ii):
Saturated aqueous hydrogen sulfide has a concentration of 0.10 mol dm−3 and a pH of 4.0. Demonstrate whether it is a strong or weak acid.
-
20N.1.sl.TZ0.20:
Which of these acids has the weakest conjugate base?
A.
B.
C.
D.
- 20N.2.sl.TZ0.1c(i): Hypochlorous acid is considered a weak acid. Outline what is meant by the term weak acid.
- 20N.2.hl.TZ0.1c(i): Hypochlorous acid is considered a weak acid. Outline what is meant by the term weak acid.
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17M.3.sl.TZ2.14b.i:
Oceans can act as a carbon sink, removing some CO2(g) from the atmosphere.
CO2(g) CO2(aq)
Aqueous carbon dioxide, CO2(aq), quickly reacts with ocean water in a new equilibrium reaction. Construct the equilibrium equation for this reaction including state symbols.
- 21N.1.sl.TZ0.20: Which ions are present in an aqueous solution of Na2CO3? I. HCO3−II. OH−III. CO32− A. I...
