2025 ZHSS Sc(Chem) Prelim P1 (with MS)

1 21 Which pair of apparatus must be used in obtaining dry samples of both a soluble salt and an insoluble salt from a mixture of the two salts in water? A evaporating dish and measuring cylinder B evaporating dish and filter funnel C filter funnel and measuring cylinder D filter funnel and stopwatch 22 The diagram shows a chromatogram of a food colouring. Which two colours does the food colouring contain? A 1 and 2 B 2 and 3 C 3 and 4 D 4 and 5 23 Which row correctly describes the particles of sugar molecules and water molecules in a dilute sugar solution at room temperature? sugar molecules water molecules A closely packed, moving at random closely packed, moving at random B closely packed, not moving far apart, moving at random C far apart, moving at random closely packed, moving at random D far apart, moving at random far apart, moving at random

2 24 Which diagram represents a mixture of diatomic elements? A B C D 25 Carbon has three naturally occurring isotopes: carbon-12, carbon-13 and carbon-14. Which statement about carbon-14 is correct? A It has the same number of neutrons as protons. B It has the same number of protons than carbon-13. C It has the same relative atomic mass as carbon-13. D It is formed by the addition of 2 electrons to carbon-12. 26 The diagram shows the structure of hydrogen peroxide. What is the total number of electrons used for bonding in this molecule? A 3 B 4 C 6 D 8 27 The proton and nucleon numbers of P and Q are shwn. element proton number nucleon number P 3 7 Q 8 16 What is the relative formula mass of the compound formed by the elements P and Q? A 23 B 30 C 39 D 46

3 28 The equation for the production of ammonia is given below: N2 (g) + 3H2 (g)  2NH3 (g) 2 moles of nitrogen gas is mixed with 7 moles of hydrogen. What will be present after the reaction? A 2 moles of ammonia B 2 moles of ammonia and 1 mole of nitrogen C 4 moles of ammonia D 4 moles of ammonia and 1 mole of hydrogen 29 Which statement is correct for 22 g of carbon dioxide? A It contains 1.51 × 10²³ carbon atoms. B It contains 1.51 × 10²³ oxygen atoms. C It contains 6.02 × 10²³ oxygen atoms. D It contains 6.02 × 10²³ carbon dioxide molecules. 30 One mole of compound X gives 3 moles of ions in aqueous solution. X reacts with ammonium carbonate to give an acidic gas. What is compound X? A calcium hydroxide B hydrochloric acid C sodium hydroxide D sulfuric acid

4 31 Which equation does not represent a redox reaction? A Ba2+ (aq) + SO42– (aq)  BaSO4 (s) B Br2 (g) + 2I– (aq)  2Br– (aq) + I2 (s) C Cl2 (g) + S2– (aq)  S (s) + 2Cl– (aq) D Cu2+ (aq) + Zn(s)  Cu (s) + Zn2+ (aq) 32 Aqueous ammonium sulfate is tested with aqueous sodium hydroxide and then warmed gently. Which observation can be made? A A gas is produced that bleaches damp red litmus paper. B A gas is produced that turns damp r