5.5 Tests for Anions Flashcards

1
Q

What do “qualitative tests” mean when referring to testing for ions?

A

Measuring the colour of a precipitate

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What do “quantitative tests” mean when referring to testing for ions?

A

Titrations, which measure numerical data and let you work out the amount of a substance in a sample

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

How should you choose your samples when testing water in an area?

A

You should take samples in slightly different places and test them all.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

How should you choose your samples when testing a chemical that’s been made in industry?

A

You should take a number of samples at random from each batch to test.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

When testing the purity of a substance you’ve crystallised by testing its melting point, why should you take a couple samples?

A

In case there’s some variation across the substances.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

How do you test for carbonates? (3)

A
  • To test for carbonate ions in solution, add some dilute acid.
  • If there are carbonate ions present, the mixture will fizz - this is because the carbonate will react with the acid to produce carbon dioxide gas.
  • You can check to see if a gas is carbon dioxide by bubbling it through limewater. If it is carbon dioxide, the limewater turns cloudy.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

How do you test for sulfates? (2)

A
  • To test for sulfate ions in solution, first add some dilute hydrochloric acid to the test sample - this stops any precipitation reactions not involving sulfate ions from taking place.
  • Then add some barium chloride or barium nitrate solution. If there are sulfate ions in the solution, a white precipitate of barium sulfate will form.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

How do you test for halide ions?

A

To test for chloride ions, bromide ions or iodide ions, add some dilute nitric acid to get rid of carbonate and sulfate impurities, followed by a few drops of silver nitrate solution. The silver ions from the silver nitrate react with the halide ions to form a precipitate.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What does a positive test for chloride look like?

A

A chloride gives a white precipitate of silver chloride.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What does a positive test for bromide look like?

A

A bromide gives a cream precipitate of silver bromide.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What does a positive test for iodide look like?

A

An iodide gives a yellow precipitate of silver iodide.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What does the term ‘anion’ mean?

A

A negatively charged ion

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

A chemical reaction is taking place in a test tube. What methods could be used to collect the gas?

A
  • Attach the top of the test tube to a gas syringe.
  • Place an upside down measuring cylinder over the test tube to trap the gas.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

When testing for sulfate ions, why do we have to add hydrochloric acid first?

A

To react with any carbonate ion impurities

How well did you know this?
1
Not at all
2
3
4
5
Perfectly