Rp4 inorganic tests

Question 1

group 2 metals test method (NaOH) method

Answer 1

1.10 drops 0.1 mol BaCl2
2.then 10 drops 0.6 mol NaOH
3.add NaOH in Excess

After step 1 all solutions are a Colourless sol

BaCl2 - Colourless sol for all
CaBr2 - 2/3. slight white ppt
SrCl2 - 2/3. slight white ppt
MgCl2- 2. slight white ppt , 3. white ppt

Question 2

group 2 metals test method (H2SO4 method)

Answer 2

1.10 drops of 0.1 mol BaCl2 then add 10 drops of 1.0 mol H2SO4
2. add H2SO4 in excess

BaCl2 -1/2. White ppt
CaBr2 -1/2 slight white ppt
SrCl2 - 1/2 white ppt
MgCl2- 1. slight white ppt 2. colourless sol

Question 3

group 2 metals with ammonium solution

Answer 3

all remain a colourless solution
Apart From Mg2+ ions - white ppt of Mg(OH)2

Question 4

test for ammonium ions

Answer 4

10 drops ammonium chloride and NaOH
Warm the mixture in a test tube with the above solution in a W.B - gentle warming since ammonia gas very soluble
Test Damp red Litmus paper above it

Positive result = litmus paper turns blue since ammonium ions are basic

Question 5

test for OH hydroxide ions

Answer 5

1 cm depth of solution in a test tube with red litmus paper

positive result= blue

Question 6

Test for OH- hydroxide ions ( ammonia)

Answer 6

5 drops of 1.0 NH3 sol on filter paper in a petri dish, add damp red litmus on the other side. Close lid.

positive result = blue litmus

Question 7

Test for carbonate ions

Answer 7

Add dilute HCl to sodium carbonate solution.
Use a delivery tube to bubble gas into limewater.
Stopper the limewater test tube.

If carbonate ions present, limewater turns cloudy.

Na₂CO₃ + 2HCl → 2NaCl + H₂O + CO₂
Ca(OH)₂ + CO₂ → CaCO₃ + H₂O

Question 8

Test for sulphate ions

Answer 8

Add dilute HCl, then barium chloride to the solution.
White precipitate = barium sulfate (insoluble).
Add some dilute HCl.

If precipitate doesn’t dissolve, sulfate or hydrogensulfate ions present.
MgSO₄ + BaCl₂ → BaSO₄ (s) + MgCl₂ (aq)

Question 9

Test for halide ions in Aqueous solution

Answer 9

Add dilute nitric acid to potassium halide solution (removes unwanted ions).
1.Add silver nitrate + observe precipitate.
Swirl, split sample in two.
2.add dilute ammonia to one half, observe.
3. Add conc NH3 to other half (in fume cupboard), observe.
Repeat for KBr and KI.

KI gives a yellow ppt in all cases
KBr gives cream ppt for 1/2 and gives colourless sol for 2
KCl gives white ppt for 1. and colourless sol for 2/3

Question 10

Test for solid salts of group 7

Answer 10

add conc H2SO4
KCl - White, steamy fumes
KBr - Orange fumes
KI - Purple fumes and purple/black solid

all turn BLUE litmus RED