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Cambridge IGCSE™
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CHEMISTRY 0620/42
Paper 4 Theory (Extended) February/March 2025
1 hour 15 minutes
You must answer on the question paper.
No additional materials are needed.
INSTRUCTIONS
● Answer all questions.
● Use a black or dark blue pen. You may use an HB pencil for any diagrams or graphs.
● Write your name, centre number and candidate number in the boxes at the top of the page.
● Write your answer to each question in the space provided.
● Do not use an erasable pen or correction fluid.
● Do not write on any bar codes.
● You may use a calculator.
● You should show all your working and use appropriate units.
INFORMATION
● The total mark for this paper is 80.
● The number of marks for each question or part question is shown in brackets [ ].
● The Periodic Table is printed in the question paper.
This document has 12 pages.
DC (WW/FC) 341207/6
© UCLES 2025 [Turn over
, * 0000800000002 *
DO NOT WRITE IN THIS MARGIN
2
, ,
1 Using numbers only, state the:
(a) percentage of oxygen in clean, dry air ............................... [1]
(b) typical operating temperature, in °C, used in the Haber process ............................... [1]
(c) number of atoms in a diatomic molecule ............................... [1]
(d) maximum number of electrons in the second electron shell of an atom ............................... [1]
(e) number of hydrogen atoms in an alkane with 7 carbon atoms ............................... [1]
DO NOT WRITE IN THIS MARGIN
(f) number of particles in one mole, in standard form. ............................... [1]
[Total: 6]
2 This question is about ionic compounds.
(a) State what is meant by the term ionic bond.
...................................................................................................................................................
DO NOT WRITE IN THIS MARGIN
............................................................................................................................................. [2]
(b) Potassium sulfide, K2S, is an ionic compound.
Complete the dot-and-cross diagram in Fig. 2.1 of the ions in potassium sulfide.
Show the charges on the ions.
..... ..... .....
DO NOT WRITE IN THIS MARGIN
K S K
Fig. 2.1
[3]
DO NOT WRITE IN THIS MARGIN
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© UCLES 2025 ĬÝĠûÖĠýāÏîāĝ¸äÊĊĈĂ
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0620/42/F/M/25
, ,
Cambridge IGCSE™
¬Wz> 4mHuOªE`y6W
¬]|W¬§hwZz2
¥eE55Eu¥EE 5eUEU
* 3 9 0 1 0 0 1 6 5 1 *
CHEMISTRY 0620/42
Paper 4 Theory (Extended) February/March 2025
1 hour 15 minutes
You must answer on the question paper.
No additional materials are needed.
INSTRUCTIONS
● Answer all questions.
● Use a black or dark blue pen. You may use an HB pencil for any diagrams or graphs.
● Write your name, centre number and candidate number in the boxes at the top of the page.
● Write your answer to each question in the space provided.
● Do not use an erasable pen or correction fluid.
● Do not write on any bar codes.
● You may use a calculator.
● You should show all your working and use appropriate units.
INFORMATION
● The total mark for this paper is 80.
● The number of marks for each question or part question is shown in brackets [ ].
● The Periodic Table is printed in the question paper.
This document has 12 pages.
DC (WW/FC) 341207/6
© UCLES 2025 [Turn over
, * 0000800000002 *
DO NOT WRITE IN THIS MARGIN
2
, ,
1 Using numbers only, state the:
(a) percentage of oxygen in clean, dry air ............................... [1]
(b) typical operating temperature, in °C, used in the Haber process ............................... [1]
(c) number of atoms in a diatomic molecule ............................... [1]
(d) maximum number of electrons in the second electron shell of an atom ............................... [1]
(e) number of hydrogen atoms in an alkane with 7 carbon atoms ............................... [1]
DO NOT WRITE IN THIS MARGIN
(f) number of particles in one mole, in standard form. ............................... [1]
[Total: 6]
2 This question is about ionic compounds.
(a) State what is meant by the term ionic bond.
...................................................................................................................................................
DO NOT WRITE IN THIS MARGIN
............................................................................................................................................. [2]
(b) Potassium sulfide, K2S, is an ionic compound.
Complete the dot-and-cross diagram in Fig. 2.1 of the ions in potassium sulfide.
Show the charges on the ions.
..... ..... .....
DO NOT WRITE IN THIS MARGIN
K S K
Fig. 2.1
[3]
DO NOT WRITE IN THIS MARGIN
ĬÕú¾Ġ´íÈõÏĪÅĊÝû¸þ×
© UCLES 2025 ĬÝĠûÖĠýāÏîāĝ¸äÊĊĈĂ
ĥõÕĕõÕąĕååĕąąõÅĕĥÕ
0620/42/F/M/25
