Q Rubric Marks1 (a) [Able to record the time at 1 decimal place accurately]

50.0 s, 48.0 s, 42.0 s, 37.0 s, 33.0 s3

No unit / No decimal place/ wrong 1 reading 2Wrong 2 readings 1More than 2 wrong readings 0

1 (b) [Able to write the correct balanced equation]Na2S2O3 + H2SO4 Na2SO4 + SO2 + S + H2O

3

Correct reactants and products but not balanced 2At least 5 reactants/products correct 1Wrong response or no response 0

1 (c) [Able to construct a table to record temperature, time and 1/time with units accurately](1/time 3 dp)

Temperature (oC)

30 35 40 45 50

Time (s) 50.0 48.0 42.0 37.0 33.01/time (s-1) 0.020 0.021 0.024 0.027 0.030

3

Wrong dp for 1/time 2At least 4 correct 1/time values 1Wrong or no response 0

1 (d)(i)

[Able to plot a graph of temperature against 1/time , axis with unit and uniform scale ]

0.018 0.02 0.022 0.024 0.026 0.028 0.03 0.03225

30

35

40

45

50

55

1/time (s-1)

Tem

pera

ture

(oC)

3

Able to transfer at least 4 points correctly 2Able to transfer at least 3 points correctly 1Wrong or no response 0

1 (d)(ii)

The higher the temperature, the higher the rate of reaction 3The rate of reaction is linearly proportional to the temperature 2The rate of reaction depends on the temperature 1Wrong response or no response 0

1 (e)Type of variable Action that needs to be takenManipulated variableTemperature of sodium thiosulphate solution

The solution is heated to the required temperature

RespondingThe time taken for the x mark to disappear

The time taken for the x mark to disappear is recorded

Fixed variableConcentration, volume

Use the same concentration/volume of sodium thiosulphate throughout the experiment

3

Able to state 2 variables correctly 2Able to state 1 variable correctly 1Wrong response or no response 0

2 (a)(i)

Mg + Cu2+ Mg2+ + Cu 321

Wrong response or no response 02 (a)(ii)

Magnesium dissolves to form Mg2+ ions 3Magnesium ions are produced 2Magnesium metal corrodes / becomes smaller 1Wrong response or no response 0

2 (b) 1.10-0.45 = 0.65 3Higher than 0.45 lower than 1.10 2

1Wrong response or no response 0

2 (c) Copper, lead, iron, zinc, magnesium 3At least 4 in correct order 2At least 3 in correct order 1Wrong response or no response 0

2 (d) When pair of metals are further apart in the ecs is dipped in an electrolyte, a higher voltmeter reading is obtained

3

21

Wrong response or no response 0

3 (a) To prepare ethyl ethanoate, ester 1, and pentyl butanoate, ester 2 3To prepare ester 1 and ester 2 2To prepare ester 1Wrong response or no response 0

3 (b) Manipulated : alcohol and carboxylic acidResponding : Ester producedFixed : Presence of catalyst, concentrated sulphuric acid

3

Able to state 2 correctly 2Able to state 1 correctly 1Wrong response or no response 0

3 (c) Apparatus : Test tube , beakersMaterials : ethanol, pentanol, glacial ethanoic acid, butanoic acid, concentrated sulphuric acid

3

Able to state 5 apparatus / materials correctly 2Able to state 4 apparatus/ materials correctly 1Wrong response or no response 0

3 (d) 1. 2 cm3 of glacial ethanoic acid is placed into a test tube2. 4 cm3 of ethanol is added to the ethanoic acid3. About 1 cm3 of sulphuric acid is added slowly and carefully to the mixture

using a dropper4. The reaction mixture is shaken and heated slowly for about 3 minutes5. The content of the test tube is then poured into a beaker half-filled with

water.6. The physical properties of the ester is observed and recorded7. The process is repeated using pentanol and butanoic acid

3

Able to state 6 procedures correctly 2Able to state 5 procedures correctly 1Wrong response or no response 0

1 (e)Ester 1 Ethyl ethanoate 2 pentyl butanoateSmell Sweet / fruity Sweet/ fruitySolubility in water insoluble Insolublevolatility volatile volatile

3

Ester 1 2Smell Sweet / fruity Sweet/ fruitySolubility in water insoluble Insolublevolatility volatile volatile

2

Smell Sweet / fruitySolubility in water insolublevolatility volatile

1

Wrong response or no response 0