CHEMISTRY FORM 4STANDARDIZED TEST 1 SEMESTER 2 2015

ANSWER SCHEMESECTION A : OBJECTIVE

1 2 3 4 5 6 7 8 9 10D C C A D A C C A D11 12 13 14 15 16 17 18 19 20C D D B B B C D A C

SECTION B : STRUCTUREQuestion No Answer Mark

1. (a) The number of valence electrons in each atom increases from 1 to 8

Therefore, nuclei attraction on the electrons increases across Period 3.

1

1(b) Increases 1(c) Silicon / Si 1(d) Soft metals / Silvery and shiny surfaces / Low melting and

boiling points as compared to other metals such as iron and copper / Low densities / Good conductors of heat and electricity 1

(e) i Aluminium / Al

Show both acidic and basic properties

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1ii Sodium / Na 1

(f) Cl2 + H2O HCl + HOCl

Correct reactantsCorrect products

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TOTAL 102. (a) (i) Na+, Cl-, H+, OH-

a: name1

(ii) Cl-Concentration of Cl- is higher than OH- in the electrolyte

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(iii) 2Cl- Cl2 + 2e 1(b) i -functional diagram

- label11

ii - collect the gas released in the test tube- put a lighted wooden splinter at the mouth of the test tube- if ‘pop’ sound is produced confirm the presence of H2 gas

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1

Iii - Na+ and H+ will attracted to cathode- H+ will discharged by accepting 2 electrons to form

H2 // 2H+ + 2e H2

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TOTAL 11SECTION C : ESSAY

1. (i) - Correct the formulae of reactants and products- Balance the chemical equation- Eg: 2 J + 2 H2O 2 JOH + H2

[ a: Na ]

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(ii) 1) Atom K is more reactive than atom J2) number of proton of atom K is more than atom J3) The distance between nucleus and electron at the outermost shell of atom K further than atom J // atomic size of K is bigger than atom J4) The attraction force between nucleus and valence electron in atom K becomes weaker than atom J5) easier for atom K to release 1 valence electron to achieve stable octet electron arrangement 6 & 7):Observation -Atom K: move very fast at random on the surface of

water and ignited and gave out “pop” sound and hissing sound.

-Atom J : moves rapidly at random on the surface of water with a hissing sound.

111

1

1

1

1

……max 6TOTAL 8

2. (a)(i) A chemical substance that can conduct electricity in molten or aqueous state and undergoes chemical changes.

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(ii) Any two suitable electrolytes 1+1 (iii) - No product form either at anode or cathode

- Glucose solution consist of molecules // no free moving ions in the solution

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(b) 1. Functional set-up of apparatus2. Label- electrolyte [CuSO4 solution], silver and magnesium.

3. Mg is more electropositive than Ag.4. Mg release electrons to form Mg2+ ions5. Electrons flow through the wire from Mg towards the Ag electrodes 6. [Cu2+] ions receive electron to form Ag atoms

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111

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TOTAL 11