IGCSE Chemistry Practical Paper 6

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Questions and Answers

State what happens to the sodium sulfate in step 1.

dissolves in water

State what is removed from the filtrate in step 3.

water

Describe what must be done after the filtrate has been heated in step 3 to obtain a larger amount of sodium sulfate crystals.

leave it to cool

State what must be done to the residue before it is allowed to dry in step 4 to obtain pure copper(II) carbonate.

wash it with distilled water Signup and view all the answers

Identify the substance removed from the copper(II) carbonate in (d)(i).

sodium sulfate Signup and view all the answers

Complete the expected observations. The student carries out a flame test on solid T.

red flame colour Signup and view all the answers

State the colour change. The student adds the first portion of solution T to a test-tube containing acidified aqueous potassium manganate(VII).

from purple to colourless Signup and view all the answers

Identify the gas produced. The gas produced turns filter paper soaked in acidified aqueous potassium manganate(VII) white.

sulfur dioxide, SO₂ Signup and view all the answers

To the solution produced in (c)(i), the student adds aqueous barium nitrate. Observations.

no change Signup and view all the answers

Identify two cations that the tests and observations in Table 3.1 show could be in solid U.

iron, chromium (B) Signup and view all the answers

Describe an additional test that the student could do to confirm which one of the two cations identified in (d) is in solid U. Give the expected result for one of the cations. Test.

add aqueous sodium hydroxide Signup and view all the answers

Describe an additional test that the student could do to confirm which one of the two cations identified in (d) is in solid U. Give the expected result for one of the cations. Cation

chromium Signup and view all the answers

Identify the anion in solid U.

iodide Signup and view all the answers

Plan an experiment to find how many water-soluble coloured compounds there are in a beetroot.

<ol> <li>crush the beetroot</li> <li>with mortar</li> <li>and water</li> <li>place a drop of the liquid on chromatography paper</li> <li>dip the bottom of the paper in water</li> <li>the number of coloured substances will be equal to the number of spots</li> </ol> Signup and view all the answers

Suggest why the measuring cylinder is inverted several times after the aqueous barium nitrate is added.

To mix the reactions and so that the concentration is uniform Signup and view all the answers

Suggest why the measuring cylinder is left to stand before the level of the precipitate is recorded.

so the precipitate can fall to the bottom Signup and view all the answers

Give a reason why burettes are used rather than measuring cylinders.

a burette is more accurate than a measuring cylinder Signup and view all the answers

Suggest why burettes are used rather than volumetric pipettes.

the volumes are not fixed Signup and view all the answers

Sketch the graph obtained if all of the experiments are repeated using aqueous barium nitrate of half the concentration used in Experiments 1 to 8.

A line that is shifted to the right, still passing through (0,0), but with a less steep slope, and the line of best fit for the last three experiments would be horizontal at a lower value on the y axis. Signup and view all the answers

Flashcards

Copper(II) Carbonate

An insoluble chemical compound used in experiments, often forming a solid residue.

Sodium Sulfate

A soluble salt that dissolves in water and forms a solution.