Ordinary level 2025 South West regional mock chemistry 1

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1. What is the change of state from gas to solid called?A. Sublimation

   B. Melting

   C. Condensation

   D. Deposition

2. Metals are malleable becauseA. They have mobile electrons

   B. The have strong metallic bond

   C. Their atoms are in layers

   D. Layers of metal atoms can slide over each other

3. What is the composition of oxygen in air?A. 0.93%

   B. 0.03%

   C. 78%

   D. 21%

4. A pure substance that cannot be broken down into simpler substances isA. A molecule

   B. An element

   C. A mixture

   D. A compound

5. Identify a crystalline allotrope of sulphurA. Colloidal sulphur

   B. Plastic sulphur

   C. Rhombic sulphur

   D. Flowers of sulphur

6. Which of the following processes undergoes a physical change?A. Heating sugar

   B. Burning paper

   C. Burning candle wax

   D. Burning wood

7. Sodium chloride allows current to pass through it, because it is.A. A conductor

   B. A non-conductor

   C. An electrolyte

   D. A non-electrolyte

Questions 8-11 concern the statement below.

The element X with isotopes X and X has relative abundances of 64% and 36% respectively.

Deduce the neutron number of the two isotopes.

15

17

16

16

A. 16 and 16

B. 15 and 17

C. 16 and 15

D. 16 and 17

9. What is the relative atomic mass of X?

A. 15.00

B. 16.72

C. 31.72

D. 32.28

10. What type of bonding will occur oxygen?A. Covalent

    B. Ionic

    C. Metallic

11. Why is calcium chloride used as a drying agent?

Questions 12-13 concern the following conversions

C2H4

b

CH3COOH

c

C2H5OH

12. State the reaction condition represented by b.A. Conc.

    H2​SO4​ in excess

    B. Dil.

    H2​SO4​ in excess

    C. Conc. HCl in excess

    D. Conc.

    H2​SO4​ /K2​Cr2​O7​

13. Identify the reagent cA.

    Cl2​

    B.

    H2​

    C. Pt

    D. Ni

14. From the thermochemical equation

    C2​HS​OH(g)+O2​(g)→CO2​(g)+H2​O(l)ΔH⇒−1339Kj

    What does the negative sign of ΔH signify?

    A. Heat is evolved

    B. Reaction is endothermic

    C. Heat flows from the surrounding to system

    D. The reaction is not reversible

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