Experimental chemistry - Chemistry - page 267

8 E numbers identify chemicals which are added to
foods.
a E210 is benzoic acid. How could you show
that a solution of benzoic acid is a weak acid?
test ______
result ______

Test Observation

Tests on solid S
a Appearance of solid S black solid

b Hydrogen peroxide was added
to solid S in a test-tube.

slow effervescence

[2]

A glowing splint was inserted
into the tube.

splint relit

b E211 is sodium benzoate. Name a suitable
substance that would react with a solution of
benzoic acid to form sodium benzoate. [1]
c E110 is Sunset Yellow. Outline a method you
could use to show the presence of E110 in a
food colouring. A space has been left if you
want to draw a diagram to help answer the
question. [4]
[Total: 7]
(Cambridge IGCSE Chemistry 0620 Paper 61
Q7 November 2010)

c Dilute sulfuric acid was added
to solid S in a test-tube. The
mixture was heated to boiling
point.

blue solution formed

The solution was divided into
three equal portions into test-
tubes.

(i) To the first portion of the
solution, excess sodium
hydroxide was added.

. . . . . . . . . . . . . . . . . . . [1]

(ii) To the second portion of the
solution, about 1 cm of aqueous
ammonia solution was added.

. . . . . . . . . . . . . . . . . . . [2]

9 Describe a chemical test to distinguish between
each of the following pairs of substances.
An example is given.
Example: hydrogen and carbon dioxide
test lighted splint
result with hydrogen gives a pop
result with carbon dioxide splint is extinguished
a zinc carbonate and zinc chloride
test ______
result with zinc carbonate ______
result with zinc chloride ______

. . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . Excess ammonia solution was

then added.

[2]

(iii) To the third portion of the
solution, dilute hydrochloric
acid was added followed by
barium chloride solution.

. . . . . . . . . . . . . . . . . . . [2]

Tests on solid V
d Appearance of solid V black solid

e Hydrogen peroxide was added
to solid V in a test-tube.

rapid effervescence

[2]

A glowing splint was inserted
into the tube.

splint relit

b ammonia and chlorine
test ______
result with ammonia ______
result with chlorine ______ [3]
c aqueous iron( ii ) sulfate and aqueous iron(ii) iii )
sulfate
test ______
result with aqueous iron( ii ) sulfate ______
result with aqueous iron( iii ) sulfate ______ [3]
[Total: 8]
(Cambridge IGCSE Chemistry 0620 Paper 06
Q3 June 2009)

f (i) Compare the reactivity of solid S and
solid V with hydrogen peroxide. [1]

(ii) Identify the gas given off in test (e) . [1]

g What conclusions can you draw about
solid V ? [2]
[Total: 11]
(Cambridge IGCSE Chemistry 0620 Paper 06
Q5 June 2009)

11 Acid base indicators
Indicators are used to identify acids and bases.
Indicators can be obtained from berries and other
fruits.
a Plan an experiment to obtain an aqueous
solution of an indicator from some berries. [3]
b Plan an experiment to use the indicator
solution to show that it is an effective
indicator. [3]
[Total: 6]
(Cambridge IGCSE Chemistry 0620 Paper 06
Q6 June 2009)

10 Two solids, S and V , were analysed. S was
copper( ii ) oxide.
The tests on the solids, and some of the
observations, are in the following table.
Complete the observations in the table. Do not
write any conclusions in the table.