Carbonate,Halide And Sulfate Tests

Question 1

What carbonate ion do all carbonates contain?

Answer 1

CO3^-2

Question 2

How do you test for the presence of a carbonate?

Answer 2

Add a dilute acid eg HCl and test the gas that is released by bubbling through limewater. If there are carbonate compounds, the calcium carbonate should turn cloudy white due to the precipitate.

Question 3

What is a halide ion?

Answer 3

A negative ion (anion) formed by the elements in group 7.

Question 4

What halide ions do you test for?

Answer 4

Chloride ions (Cl-)
Bromide (Br-)
Iodide (I-)

Question 5

How do you test for a halide ion?

Answer 5

• add dilute nitric acid to the unknown halide solution to remove impurities from the mix.
• add silver nitrate solution
• the silver and halide ions will react to form differing precipitates.

Question 6

What colour is the silver chloride precipitate?

Answer 6

White

Question 7

What colour is the silver bromide precipitate?

Answer 7

Cream

Question 8

What colour is the silver iodide precipitate?

Answer 8

Yellow

Question 9

How do you test for sulfate ions?

Answer 9

SO4^2- ions can be tested for by:
- add dilute hydrochloride acid to a tube of the sample (that may be a sulfate)
- add aqueous barium chloride solution.

Question 10

How do you know whether a sulphate is present or not?

Answer 10

A white precipitate forms.