The Laboratory Challenge

Lab Challenge 4

Modified GCE `O' Level Chemistry Practical

Observe the following demo experiment on solid R and solution S. Record your observations in the table given. You should identify and name any gas evolved.

Solid R
Solution S

Test
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Observations
1) Put half of your sample of R into a hard glass tube and heat strongly until no further change is observed. You should test for the gas evolved. Allow the residue to cool.

View experiment 1a

View experiment 1b

View experiment 1c

View experiment 1d

1a)
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Solution S has been prepared for you by dissolving the residue from Test 1 in dilute nitric acid. Use solution S for Tests 2 and 3.


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2a) To a portion of solution S, add aqueous sodium hydroxide until a change is seen

b) Add excess aqueous sodium hydroxide to the mixture from(a).

2a)
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2b)
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3) To a portion of solution S, add aqueous potassium iodide.

3)
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4a) To a portion of solid R, add a small volume of dilute sulphuric acid followed by an equal volume of aqueous potassium iodide. Allow the mixture to stand for a few minutes.

b) Pour off some of the solution from (a) into a clean test tube and then add an equal volume of aqueous sodium thiosulphate.

View experiment 4a

View experiment 4b

4a)
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4b)
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5) To a portion of solid R, add a small volume of concentrated hydrochloric acid and leave to stand for a few minutes, shaking occasionally.

5)
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When the reaction in Test 5 has stopped, add distilled water until the test-tube is about half full. Allow any solid to settle and pour off the solution into a clean test-tube and use this solution for Tests 6 and 7.


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6a) To a portion of solution from Test 5, add aqueous sodium hydroxide until a change is seen.

b) Add excess aqueous sodium hydroxide to the mixture from(a).

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6a)
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6b)
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7a) To a portion of solution of solution from Test 5, add a few drops of aqueous potassium iodide.

b) Add excess aqueous potassium iodide to the mixture from (a).

View experiment 7a

View experiment 7b

7a)
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Conclusions

Solid R contains two elements.

The non-metallic element in R is

Give one property of R and the number of the test which suggests this property.

Property of R Test Number

 


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