Question
The diagrams show part of the structures of five substances, $\mathbf{A}, \mathbf{B}, \mathbf{C}, \mathbf{D}$ and $\mathbf{E}$.
(a) Answer the following questions about these structures.
Each structure may be used once, more than once or not at al
l.
(i) Which two of these structures, $\mathbf{A}, \mathbf{B}, \mathbf{C}, \mathbf{D}$ or $\mathbf{E}$, are covalently bonded? [2]
(ii) Which one of these structures, $\mathbf{A}, \mathbf{B}, \mathbf{C}, \mathbf{D}$ or $\mathbf{E}$, is a diatomic molecule? [1]
(iii) Which one of these structures, $\mathbf{A}, \mathbf{B}, \mathbf{C}, \mathbf{D}$ or $\mathbf{E}$, is a compound? [1]
(iv) Which one of these structures, $\mathbf{A}, \mathbf{B}, \mathbf{C}, \mathbf{D}$ or $\mathbf{E}$, is very soluble in water? [1]
(v) Which one of these structures, $\mathbf{A}, \mathbf{B}, \mathbf{C}, \mathbf{D}$ or $\mathbf{E}$, is used in cutting tools? [1]
(vi) Which one of these structures, $\mathbf{A}, \mathbf{B}, \mathbf{C}, \mathbf{D}$ or $\mathbf{E}$, is used in electrical wiring? [1]
(b) Substance $\mathbf{B}$ is an element.
What is meant by the term element? [1] [Total: 8]
▶️Answer/Explanation
Ans:
(a)(i) B / diamond (1)
D / nitrogen / N2 (1)
(a)(ii) D / nitrogen / N2
(a)(iii) C / lithium chloride / LiCl
(a)(iv) C / lithium chloride / LiCl
(a)(v) B / diamond
(a)(vi) E / copper / Cu
(b) substance in which all the atoms have the same proton number / substance containing (only) one type of atom
Question
(a) Biogas is a mixture of gases produced when agricultural waste is broken down in the absence of oxygen.
The table compares the percentage by mass of the gases present in two samples of biogas, X and Y.
Answer these questions using only the information in the table.
(i) Deduce the percentage by mass of the other gases in biogas X.[1]
(ii) Describe two major differences in the compositions of biogas X and biogas Y.[2]
1
2
(b) Complete the diagram to show the electronic structure in a methane molecule.
Show only the outer shell electrons.[1]
(c) Hydrogen sulfide burns in air to produce sulfur dioxide and water.
(i) Complete the chemical equation for this reaction.
…..H2S + …..O2 → 2H2O + 2SO2 [2]
(ii) Explain how this equation shows that hydrogen sulfide is oxidized.[1] [Total: 7]
Answer/Explanation
Ans:
(a)(i) 1 (%)
(a)(ii) 1 mark each for any two of:
-
-
- less carbon dioxide in X / more carbon dioxide in Y
- more methane in X / less methane in Y
- less nitrogen in X / more nitrogen in Y
-
(b) 2 electrons in each of the four overlap areas
AND
no unpaired electrons on the hydrogen atoms
(c)(i) 2 (H2S) (1)
3 (O2) (1)
(c)(ii) sulfur has gained oxygen / hydrogen sulfide has gained oxygen
Question
This question is about elements in the Periodic Table.
(a) The table shows some properties of five elements, P, Q, R, S and T.
Use only the elements shown in the table to answer this question.
State which two of the elements, P, Q, R, S and T, are covalent molecules.
Give two reasons for your answer.
elements …………………………………………………….. and ……………………………………………………..
reason 1 …………………………………………………………………………………………………………………….
reason 2 …………………………………………………………………………………………………………………….
(b) Element T is on the left-hand side of the Periodic Table.
Suggest whether its oxide is acidic or basic.
Give a reason for your answer.
(c) Krypton is an element in Group VIII of the Periodic Table.
Explain, using ideas about electronic structure, why krypton is unreactive.
(d) Sodium is an element in Group I of the Periodic Table. Iron is a transition element.
Iron has a higher melting point and higher boiling point than sodium.
Give two other ways in which the properties of transition elements differ from the properties of
Group I elements.
1 ……………………………………………………………………………………………………………………………….
2 ……………………………………………………………………………………………………………………………….
(e) The table compares the reactivity of four metals with dilute hydrochloric acid.
Put the four metals in order of their reactivity.
Put the least reactive metal first.
(f) Hot iron reacts with steam. The reaction is reversible.
Complete the equation by writing the symbol for a reversible reaction in the box.
(g) Steel is an alloy of iron.
State the meaning of the term alloy.
Answer/Explanation
Answer:
(a) Q AND S (1)
low melting points (1)
poor conductor (of electricity) / does not conduct (electricity) (1)
(b) basic (oxide) AND
T is a metal / metal oxides are basic
(c) has a complete outer (electron) shell / has a full outer (electron) shell
(d) 1 mark each for any 2 of:
• transition elements have a high(er) density / Group I has a low(er) density
• transition elements form coloured compounds / Group I compounds are not coloured
• transition elements form ions with different charges / Group I forms only one type of ion
• transition elements are good catalysts / Group I elements not catalysts
(e) copper < nickel < iron < calcium (2)
if 2 marks not scored, 1 mark for:
1 consecutive pair reversed / calcium < iron < nickel < copper
(f) \(\leftrightarrow \)
(g) mixture of metal with another element