tests

Question 1

a few drops of NaOH

Answer 1

Zn2+, Al3+, Pb2+, Ca2+ –> white ppt
NH4 + : No ppt. on heating ammonia gas is given off: turns moist red litmus paper blue
Cu2+ :Light blue ppt
Fe2+: Green ppt
Fe3+: Reddish-brown ppt

Question 2

Excess NaOH

Answer 2

Zn2+, Al3+, Pb2+: white ppt dissolves in excess NaOH to form a colourless solution
Ca2+, Cu2+, Fe2+, Fe3+: ppt insoluble in excess
NH4+:No change is observes

Question 3

A few drops of aqueous NH3, ammonia

Answer 3

Zn2+, Al3+, Pb2+: white ppt
Fe2+:Green ppt
Fe3+: Reddish-brown ppt
Cu2+: Light blue ppt
Ca2+ , NH4 +: no ppt

Question 4

Excess NH3 aq

Answer 4

Zn2+: Ppt dissolves in excess to form a colourless solution
Al3+, Pb2+, Fe2+, Fe3+ : Ppt is insoluble in excess
Cu2+: Ppt dissolves in excess to form a deep blue solution

Question 5

CO3 2- test

Answer 5

1. Add dilute hydrochloric acid–> effervescence observed
2. pass the gas given off into limewater –> gas given off forms a white ppt with limewater. carbon dioxide gas is given off

Question 6

NO3-

Answer 6

1. Add sodium hydroxide solution, then add a piece of aluminium foil. Warm the mixture. Effervescence is observed.
2. Test the gas given off with a piece of moist red litmus paper– Moist red litmus paper turned blue. Ammonia gas is given off.

Question 7

SO42-

Answer 7

1. Add dilute nitric acid
2. Add barium nitrate solution
   - White ppt formed(barium sulfate)

Question 8

Cl-

Answer 8

1. Add dilute nitric acid
2. Add silver nitrate solution
   - White ppt formed (silver chloride)

Question 9

Cl2(g)

Answer 9

-greenish-yellow gas with a pungent smell
Test: place a piece of moist blue litmus paper at the mouth of the test tube – moist blue litmus paper turns red and is then bleached

Question 10

CO2(g)

Answer 10

Bubble gas through limewater, a white ppt is formed

Question 11

O2(g)

Answer 11

Inset a glowing splint into the test tube. The glowing splint is rekindled.

Question 12

H2(g)

Answer 12

Place a lighted splint into the test tube
- the lighted splint is extinguished with a ‘pop’ sound.

Question 13

SO2(g)

Answer 13

Pungent smell
Place a piece of filter paper soaked with acidified potassium manganate (VII) at the mouth of the test tube.
Purple acidified potassium manganate (VII) turns colourless.

Question 14

NH3 (g)

Answer 14

Place a piece of moist red litmus paper at the mouth of the test tube: moist red litmus paper turns blue.

Question 15

Water test

Answer 15

Heat the sample in a test tube. Place a piece of cobalt (II) chloride paper at the mouth of the test tube – Cobalt (II) chloride paper changes from blue to pink.
OR
Add a few drops of anhydrous copper (II) sulfate – anhydrous copper (II) sulfate turns from white to blue

Question 16

Reducing agent test

Answer 16

For solutions: Add acidified potassium manganate (VII) KMnO4 to the unknown solution - the colour of KMnO4 solution turns from purple to colourless
For gases: place a piece of filter paper soaked with acidified potassium manganate (VII) KMnO4 at the mouth of the test tube - acidified potassium manganate (VII) paper turns from purple to colourless.

Question 17

Oxidising agent test

Answer 17

Add aqueous potassium iodide KI to the unknown solution - a brown solution (iodide solution oxidised to form iodine by oxidising agents
OR
Dip a piece of starch-iodide paper into the unknown solution - starch-iodide paper turns from white to blue.

Question 18

Alkene test

Answer 18

Add a few drops of aqueous bromine at room temperature to the unknown compound in the absence of ultraviolet light - Red-brown liquid bromine will be decolourised if alkene is present.