C5 Test For Anions

Question 1

What do qualitative tests measure for?

Answer 1

Physical qualities such as colour.

Question 2

What do quantitative tests measure?

Answer 2

Numerical data.

They let you work out the amount of substance in a sample

Question 3

What applications do qualitative tests have?

Answer 3

Testing for chemicals in industry
Analysing the substances in rocks and soil
Testing for potentially dangerous substances in water or waste

Question 4

Why should you only test a representative sample of a substance?

Answer 4

This means you take a number of samples at random from the thing you’re testing so that you can account for any variation in its composition.

Question 5

What should you do if testing water in an area, to get a representative sample?

Answer 5

Take a number of different samples in slightly different places and test them all.

Question 6

What should you do to get a representative sample when testing a chemical that’s been made in industry?

Answer 6

Take a number of samples at random from each batch to test.

Question 7

When testing for halide ions using silver nitrate solution, why do you add nitric acid?

Why can’t you use hydrochloride acid?

Answer 7

To get rid of any carbonate ions. They produce a pale precipitate with silver nitrate too, which would confuse the results.

You can’t use hydrochloride acid, because you would be adding chloride ions.

Question 8

When testing for halide ions (chloride ions, bromide ions, iodide ions) add some dilute nitrate acid, followed by a few drops of what?

Answer 8

Silver nitrate solution

Question 9

What results do you get when testing for halide ions using silver nitrate solution for the following:

A chloride
A bromide
A iodide

Answer 9

A chloride gives a white precipitate of silver chloride

A bromide gives a cream precipitate of silver bromide

A iodide gives a yellow precipitate of silver iodide

Question 10

See p63 for chemical formulas when testing for halide ions using silver nitrate solution.

Answer 10

.

Question 11

When testing for carbonate ions in a solution what will the mixture do if there are carbonate ions present, when you add dilute acid?

Answer 11

Fizz

Question 12

Why does a mixture fizz when dilute acid is added to the mixture, when testing for carbonate ions?

Answer 12

The carbonate will react with the acid to produce carbon dioxide gas.

Question 13

How can you check to see if a gas is carbon dioxide?

Answer 13

By bubbling it through limewater. If the gas is Carbon dioxide, the limewater turns milky.

Question 14

When testing for sulfate ions in a solution, why do you add dilute hydrochloride acid to the test sample?

Answer 14

This stops any precipitation reactions not involving sulfate ions rom taking place.

Question 15

What will happen to the solution when you add barium chloride or barium nitrate, when testing for sulfate ions ?

Answer 15

A white precipitate of barium sulfate will form.

Question 16

A chemist adds some dilute nitric acid to a solution, X, followed by some silver nitrate solution. A yellow precipitate forms. What does this tell the chemist about solution X? (1 mark)

Answer 16

The solution contains iodide ions.