Chemistry 2020 Flashcards
Explain what is meant by a covalent bond.(2)
- an electrostatic attraction of two nuclei (1)
- with a shared pair of electrons(1)
State what is meant by the terms ‘relative isotopic mass’ and ‘relative atomic mass’(3)
- relative isotopic mass is the mass of an atom of
that isotope (1) - relative atomic mass is the
mean mass of an atom (1) - they both are relative to 1/12th the mass of a C-12 atom (1)
State what is meant by the term ‘isotopes’. Illustrate your answer by referring to the isotopes of potassium (2)
- atoms with the same number of protons but different numbers of neutrons (1)
- comparison between any 2 or all 3 of the 3 quoted
isotopes of potassium, referring to the correct numbers of protons and neutrons (1)
39K 19 20
40K 19 21
41K 19 22
This question is about the reactions of the halogens and halide ions.
(a) (i) When chlorine gas is bubbled through an aqueous solution of
potassium iodide, the reaction involves (1)
A oxidation only
B reduction only
C redox
D disproportionation
The only correct answer is C
A is not correct because chlorine is reduced and iodide is oxidised
B is not correct because** chlorine is reduced and iodide is oxidised**
D is not correct because** different species are oxidised and reduced**
(ii) Cyclohexane was added to the resulting solution from (a)(i). The mixture was
shaken and then allowed to stand for a few minutes. Two layers were formed.
[Density: aqueous layer solution = 1.10gcm–3, cyclohexane layer = 0.78gcm–3]
The colour of the lower layer was
(1)
A pale yellow
B purple
C red
D pale green
(b) Concentrated sulfuric acid was added to a small quantity of solid potassium iodide
in a test tube.
(i) In this exothermic reaction, which of the following mixtures of gases would be produced?
(1)
A hydrogen iodide and sulfur dioxide only
B hydrogen iodide and hydrogen sulfide only
C hydrogen iodide, sulfur dioxide and hydrogen sulfide
D hydrogen iodide, hydrogen sulfide and iodine
