Testing for negative ions ( group 7)

Question 1

Testing for sulfates ions (So4 2-) using HCl and Barium chloride

Answer 1

1 )Add hydrochloric acid and Barium chloride to substance

2) If sulfate ions are present a white precipitate of Barium sulfate forms.

Ba2+ + SO4 2- —> BaSO4

Question 2

use a pH indicator to test for hydroxides

Answer 2

1) Dip red litmus paper into the solution you are testing

2) If OH- ions are present paper will turn blue

Question 3

what do we use to test for halide ions

Answer 3

Silver Nitrate

• Cl- ions give a white precipitate of AgCl
• Br- ions give a cream precipitate of AgBr
• I- ions give a yellow precipitate of AgI

Question 4

what can we use to test for carbonates

Answer 4

Hydrochloric acid

1) Add HCl to the solution you are testing
2) If the solution contains carbonate ions then it will FIZZ.
- This is because the carbonate ions react with the hydrogen ions in the acid to give carbon dioxide.

Question 5

test for CO2 gas

Answer 5

use limewater

• bubble a gas through limewater in a test tube, if it turns cloudy carbonate ions are present. ( CO32-)

Co2 turns limewater cloudy.