Tests for ions

Question 1

Test for Carbonates

Answer 1

react with dilute acid (nitric)
positive= bubbles of gas produced (CO2)
COULD: bubble gas produced through limewater: goes cloudy

Question 2

Test for sulfates

Answer 2

Barium nitrate
Positive: formation of white precipitate
avoid using barium chloride to administer barium

Question 3

what type of reaction is the test for sulfates

Answer 3

precipitation reaction: precipitate formed from reaction between 2 solutions

Question 4

Test for halide ions

Answer 4

Silver nitrate to form a precipitate:
Cl= white, soluble in dilute NH3
Br= Cream, soluble in concentrated NH3
I= yellow, INsoluble in NH3
Add NH3 to distinguish between similar colours

Question 5

Order of testing for negative ions

Answer 5

1. Carbonate
2. Sulfate
3. Halides

Question 6

Why can we test for sulfates before carbonate

Answer 6

Carbonate ions -if present- react with barium nitrate to form white barium carbonate precipitate: masks

Question 7

why cant we test for halides before sulfates or carbonates

Answer 7

bc sulfate/carbonate ions react with silver nitrate to give white precipitates: masks

Question 8

Test for NH4+ ions

Answer 8

Add aqueous NaOH and heat gently, should release ammonia gas
Test gas released with moist pH paper, should turn blue

Question 9

What colour with NH3 gas turn moist pH paper

Answer 9

blue bc it is alkaline

Question 10

why must the ammonium solution be heated gently

Answer 10

bc the ammonia gas produced is very soluble so would not bubble out and rather dissolve in the solution if heated vigorously