| Date | November 2020 | Marks available | 1 | Reference code | 20N.1.hl.TZ0.26 |
| Level | HL | Paper | 1 | Time zone | TZ0 |
| Command term | Apply | Question number | 26 | Adapted from | N/A |
Question
Which species is a Lewis acid but not a Brønsted–Lowry acid?
A. Cu2+Cu2+
B. NH4+
C. Cu
D. CH3COOH
Markscheme
A
Examiners report
Vast majority of candidates understood the difference between Lewis and Brønsted Lowry acids.
Syllabus sections
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22M.2.hl.TZ1.4d:
Magnesium salts form slightly acidic solutions owing to equilibria such as:
Mg2+ (aq) + H2O (l) ⇌ Mg(OH)+ (aq) + H+ (aq)
Comment on the role of Mg2+ in forming the Mg(OH)+ ion, in acid-base terms.
- 17M.1.hl.TZ2.26: Which type of bond is formed when a Lewis acid reacts with a Lewis base? A. Covalent B....
- 18M.1.hl.TZ2.26: Which is an example of a Lewis base? A. an electrophile B. BF3 C. CH4 D. ...
- 22M.1.hl.TZ2.27: Which species are both Lewis and Brønsted–Lowry bases? I. CN−II. OH−III. NH3 A. I and...
- 18M.1.hl.TZ1.26: Which statements are correct? I. Lewis bases can act as nucleophiles. II....
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18M.2.hl.TZ1.5c:
Write an equation to show ammonia, NH3, acting as a Brønsted–Lowry base and a different equation to show it acting as a Lewis base.
- 22M.2.hl.TZ2.7a(i): State why NH3 is a Lewis base.
- 18N.1.hl.TZ0.26: Which species is not a Lewis base? A. OH− B. NH4+ C. H2O D. PH3
- 18N.2.hl.TZ0.9d: State, giving your reason, whether the hydroxide ion acts as a Lewis acid, a Lewis base, or...
- 19M.1.hl.TZ1.26: Which is a Lewis acid but not a Brønsted−Lowry acid? A. AlCl3 B. CH3CO2H C. HF D. CCl4
- 17N.2.hl.TZ0.3e: Describe, in terms of acid-base theories, the type of reaction that takes place between the...
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19N.2.hl.TZ0.6f(iv):
Examine the relationship between the Brønsted–Lowry and Lewis definitions of a base, referring to the ligands in the complex ion [CuCl4]2−.
-
17M.2.hl.TZ1.2e:
Describe, in terms of the electrons involved, how the bond between a ligand and a central metal ion is formed.
- 19N.1.hl.TZ0.27: Which can act as a Lewis acid but not a Brønsted–Lowry acid? A. BF3 B. H2O C. NF3 D. NH3
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19M.2.hl.TZ2.5e:
The reaction of the hydroxide ion with carbon dioxide and with the hydrogencarbonate ion can be represented by Equations 3 and 4.
Equation (3) OH− (aq) + CO2 (g) → HCO3− (aq)
Equation (4) OH− (aq) + HCO3− (aq) → H2O (l) + CO32− (aq)Discuss how these equations show the difference between a Lewis base and a Brønsted–Lowry base.
Equation (3):
Equation (4):
- 21N.2.hl.TZ0.5d: Outline the reasons that sodium hydroxide is considered a Brønsted–Lowry and Lewis base.
- 21M.1.sl.TZ1.19: Which is amphiprotic? A. NH4+ B. PO43− C. H2O D. H3O+
- 21M.2.hl.TZ1.3g: Transition metals like iron can form complex ions. Discuss the bonding between transition...
- 21M.1.hl.TZ2.26: Which is correct? A. Electrophiles are Brønsted–Lowry acids. B. Nucleophiles are...
- 22M.1.hl.TZ1.26: Which statement explains the Lewis acid–base nature of the chloride ion in this...
- 21N.2.hl.TZ0.10e: Discuss the reason benzene is more reactive with an electrophile than a nucleophile.
