Required Practical 4

Question 1

(RP.4) How do you test for Ammonium Compounds

Answer 1

Add Sodium Hydoxide to a test tube with the sample
Gently Heat the test tube
If ammonium is present, ammonia gas will be produced
Test this by placing damp red litmus paper over test tube
if litmus paper uterus blue ammonia gas is present which indicates that the ion in the salt was ammonium

Question 2

(RP.4) How do you test for magnesium salts?

Answer 2

Make a solution of the sample in a test tube
Add a few drops of Sodium Hydroxide to the test tube
Then add excess Sodium Hydroxide
If Mg2+ ions are present a white Precipitate forms

Question 3

(RP.4) How do you test for Calcium salts?

Answer 3

Dip a nichrome wire into concentrated hydrochloric acid & then into sample
Place over a blue bunsen burner flame
If the colour of the flame turns Brick-Red then calcium ions are present

Question 4

(RP.4) How do you test for Barium salts?

Answer 4

Dip a nichrome wire into concentrated hydrochloric acid & then into sample
Place over a blue bunsen burner flame
If the colour of the flame turns Green then Barium ions are present

Question 5

(RP.4) How do you test for Strontium salts?

Answer 5

Dip a nichrome wire into concentrated hydrochloric acid & then into sample
Place over a blue bunsen burner flame
If the colour of the flame turns Bright Red then Strontium ions are present

Question 6

(RP.4) How do you test for Halide ions using Silver Nitrate?

Answer 6

• Ag+(aq) + X-(aq) —> AgX(s)
  AgX +NH3 —> Ag(NH3)2+. + Cl-
• Add a Dilute Nitric Acid (HNO3) (gets rid of OH- or carbonate impurities)
• Then Add Acidified Silver Nitrate (AgNO3) + drop of sodium hydroxide (haloalkane)
  If Chlorine a white Precipitate forms
  If Bromine a Cream Precipitate Forms
  If Iodine a Yellow Precipitate Forms

Then add Ammonia (NH3)
AgCl dissolves in dilute NH3 to give a colourless solution
AgBr dissolves in concentrated NH3 to give a colourless solution
AgI is insoluble in concentrated NH3

Question 7

(RP.4) How would you test for a sulphate ?

Answer 7

1) Add HCL to remove any carbonate impurities
2) Add Barium Chloride (BaCl2)

You will Observe a white precipitate if there are sulphates present.
Ba(2+) + SO4 (2-) —> BaSO4(s)
BaCl2 + XSO4 —> BaSO4 + XCl2

Question 8

(RP.4) How do you test for a hydroxide?

Answer 8

Warm some solid Ammonium Salt with sample
Test gas produced with red litmus paper
If hydroxides are present ammonia gas is released
This changes red litmus paper to blue

Question 9

(RP.4) How do you test for a Carbonate ions?

Answer 9

Add some dilute Nitric acid into conical flask with sample
connect an airtight bung to the conical flask and a limewater reservoir
If carbonate cations are present there will be effervescence and the lime walter will turn cloudy

Question 10

Answer 10

Question 11

(RP.4) How does the following compounds react with sodium carbonate solution and sodium chloride solution

Nitric Acid
Silver Nitrate

Answer 11

Nitric Acid —-> Effervesces with sodium carbonate , No reaction with sodium chloride
Silver Nitrate —-> White PPT with sodium carbonate , White PPT eight sodium chloride

Question 12

(RP.4) How does the following compounds react with. acidified barium chloride, sodium hydroxide solution & acidified silver nitrate followed by dilute aqueous ammonia

Potassium Sulphate

Ammonium Sulphate

Potassium Iodide

Answer 12

Potassium Sulphate —> White PPT with Barium chloride solution , No reaction with sodium hydroxide solution

Ammonium Sulphate —> White PPT with Barium chloride solution ,gas released that changes red litmus paper blue, with sodium hydroxide solution

Potassium Iodide —-> No Reaction with acidified barium chloride solution, yellow precipitate with silver nitrate + Aqueous ammonia

Question 13

(RP.4) The following experiment is done:
Make solution of the sample in a test tube
Add a few drops of Sodium Hydroxide to the test tube
Then add excess Sodium Hydroxide
Describe how each of the following react

Barium Salts, Calcium Salts, Magnesium Salts and Strontium Salts.

Answer 13

Barium –> Stays a Colourless solution throughout
Calcium –> Colourless solution –> Slight White precipitate
Magnesium –> Colourless solution –> Slight White precipitate —> White precipitate
Strontium –> Colourless solution –> Slight White precipitate

Question 14

(RP.4) The following experiment is done:
Make solution of the sample in a test tube
Add a few drops of Sulphuric Acid to the test tube
Then add excess Sulphuric Acid
Describe how each of the following react

Barium Salts, Calcium Salts, Magnesium Salts and Strontium Salts.

Answer 14

Barium –> Colourless solution —> White precipitate —> White precipitate
Calcium –> Colourless solution –> Slight White precipitate
Magnesium –> Colourless solution –> Slight White precipitate —> Colourless solution
Strontium –> Colourless solution —> White precipitate —> White precipitate

Question 15

(RP.4) How would you test for an alkali

Answer 15

Dip a section of damp red litmus paper into test tube
If the submerged part turns blue then there are hydroxide ions

Question 16

(RP.4) You are testing for a Sulphate a Halide and a Carbonate on 1 Sample
In which order should you test for each ion to prevent false positive results occurring

Answer 16

Carbonate —> Sulphate —-> Halide
Prevents unexpected insoluble precipitates like Ag2SO4 Ag2CO3 and BaCO3

Question 17

(RP.4) What are the contents of the reagent for the test with halides

Answer 17

Acidified (any acid) + Silver Nitrate + Drop of Sodium Hydroxide