8.3 Qualitative analysis

Question 1

what are the different anion tests?

Answer 1

carbonate
sulfate
halide

Question 2

carbonate test

CO3 2-

Answer 2

add dilute nitric acid

bubbles of CO2 should form

Question 3

sulfate test

SO4 2-

Answer 3

add Ba(NO3)2

Ba 2+ ions will react with the SO4 2- to form BaSO4 which is insoluble

this produces a white precipitate

Question 4

halide test

Cl-
Br-
I-

Answer 4

add silver nitrate and nitric acid to a halide solution

Ag+ ions will react with the halide ions to form different coloured precipitates

Question 5

silver chloride

Answer 5

white

Question 6

silver bromide

Answer 6

cream

Question 7

silver iodide

Answer 7

yellow

Question 8

solubility of chloride

Answer 8

soluble in dilute NH3

Question 9

solubility of bromide

Answer 9

soluble in conc NH3

Question 10

solubility of iodide

Answer 10

insoluble in conc NH3

Question 11

what order should these tests be taken in?

Answer 11

carbonate
sulfate
halide

Question 12

why is the carbonate test first?

Answer 12

sulfate and halide ions dont produce CO2 when reacted with acid

Question 13

why is sulfate test second?

Answer 13

BaCO3 would be produced if a carbonate had reacted with Ba(NO3)2 first

this would also produce a white ppt so makes it harder to tell if sulfate or not

Question 14

ammonia test

NH4+

Answer 14

add aqueous NaOH which produces NH3 gas

warm to release the gas

use moist pH indicator and colour should turn from red to blue as NH3 is alkaline

Question 15

why is halide test done last?

Answer 15

produces a white precipitate with CO3 2- as well