IGCSE Chemistry solved past paper 0620/61/o/n/21

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In this video we will solve and explain Cambridge IGCSE chemistry paper 61 October/November 2021.

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Intro: (00:00)
Question1: (00:10)
A student investigated the volume of dilute sulfuric acid that would react with 25.0cm3
of aqueous
sodium carbonate.
● A burette was rinsed with water and then with dilute sulfuric acid.
● The burette was filled with dilute sulfuric acid. Some of the dilute sulfuric acid was run out of
the burette so that the level of the dilute sulfuric acid was on the burette scale.
● 25.0cm3
of aqueous sodium carbonate was poured into the apparatus labelled A in the diagram.
● Five drops of methyl orange indicator were added to the aqueous sodium carbonate in A.
● The apparatus labelled A was placed on a white tile.
● The dilute sulfuric acid was added slowly to the 25.0cm3
of aqueous sodium carbonate until
the colour of the methyl orange changed from yellow to orange.
The apparatus was arranged as shown in the diagram.

Question2: (01:55)
A student investigated the rate of reaction between small lumps of calcium carbonate and dilute
hydrochloric acid.
The experiment was done at two different temperatures using the apparatus shown in the diagram.
All other conditions were kept the same.
Experiment 1
● Using a 50cm3
measuring cylinder, 25cm3
of dilute hydrochloric acid was poured into a boiling
tube.
● The temperature of the dilute hydrochloric acid was measured using a thermometer.
● 10g of lumps of calcium carbonate were added to the boiling tube, the bung replaced and the
stop‑watch started.
● The volume of gas collected in the gas syringe was measured every 50 seconds for 250 seconds.
Experiment 2
● Using a 50cm3
measuring cylinder, 25cm3
of dilute hydrochloric acid was poured into a boiling
tube.
● The dilute hydrochloric acid in the boiling tube was warmed using a Bunsen burner.
● The temperature of the dilute hydrochloric acid was measured using a thermometer.
● 10g of lumps of calcium carbonate were added to the boiling tube, the bung replaced and the
stop‑watch started.
● The volume of gas collected in the gas syringe was measured every 50 seconds for 250 seconds.

Question3: (07:04)
Solution Y and solution Z were analysed.
The following tests were done on the solutions.
tests on solution Y
(a) Suggest the pH of solution Y.
(b) Identify solution Y.
tests on solution Z
Solution Z was aqueous ammonium sulfite.
Complete all of the expected observations.
Solution Z was divided into three portions in two boiling tubes and a test-tube.
(c) 5cm3 of dilute hydrochloric acid was added to the first portion of solution Z in a boiling
tube. The mixture was warmed and a piece of filter paper soaked in acidified aqueous
potassium manganate(VII) held at the mouth of the boiling tube.
State the colour change of the acidified aqueous potassium manganate(VII).

Question4: (10:45)
Tartrazine is used as a yellow food colouring.
Plan an investigation to find out if a yellow sweet contains tartrazine. Explain how your results will
tell you if the sweet contains tartrazine.
You have access to all normal laboratory materials, a yellow sweet and a sample of tartrazine.
You may draw a labelled diagram as part of your answer.

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