Testing For Ions

Question 1

Method for testing for CARBONATE ions

Answer 1

• Add equal amounts of HCl and NaCO3 to a tests tube
• Add bung with delivery tube to a test tube
• Delivery tube is connected to test tube with limewater (CaOH)
• CO3(2-) ions react with H+ ions to produce CO2 gas
• CO2 causes limewater to be milky

Question 2

Method for testing for SULFATE ions

Answer 2

• Add HCl then add BaCl to sample
• BaSO4 will form (white precipitate)

Question 3

Sulfate Ion

Answer 3

SO4(2-)

Question 4

Carbonate ion

Answer 4

CO3(2-)

Question 5

Halide ions

Answer 5

X(-)

Question 6

Method for testing for HALIDE ions

Answer 6

• Add sample to a test tube.
• Add HNO3 to test tube then add AgNO3

Question 7

Colours of precipitate of HALIDE test

Answer 7

No precipitate = AgF
White = AgCl
Cream = AgBr
Yellow = AgI

Question 8

Natural state/colour of CHLORINE at room tempertature

Answer 8

• Gas
• Green

Question 9

Natural state/colour of FLUORINE at room tempertature?

Answer 9

• Gas
• Yellow

Question 10

Natural state/colour of BROMINE at room tempertature?

Answer 10

• Liquid
• Brown/Red

Question 11

Natural state/colour of IODINE at room tempertature?

Answer 11

• Solid
• Grey/Black (shiny)

Question 12

Method for testing for AMMONIUM IONS

Answer 12

• Add 10 drops of sample to test tube
• Add 10 drops of NaOH to test tube and mix/swirl
• Place the test tube in a water bath and heated gently
• Hold damp red litmus paper near mouth of test tube
• Ammonia gas is produced which causes the red litmus paper to turn blue.

Question 13

Colour of CHLORINE in WATER and CYCLOHEXANE

Answer 13

Pale Green

Question 14

Colour of BROMINE in WATER and CYCLOHEXANE

Answer 14

Orange

Question 15

Colour of IODINE in WATER

Answer 15

Brown

Question 16

Colour of IODINE in CYCLOHEXANE

Answer 16

Violet

Question 17

Is ammonia gas (NH3) alkaline or acidic?

Answer 17

Alkaline

Question 18

Observations of further CHLORIDE test with AMMONIA

Answer 18

White precipitate (AgCl) dissolves in dilute ammonia solution

Question 19

Observations of further BROMIDE test with AMMONIA

Answer 19

• Cream precipitate (AgBr) is insoluble in dilute ammonia solution
• Dissolves in conc. ammonia solution

Question 20

Observations of further IODIDE test with AMMONIA

Answer 20

• Yellow precipitate (AgI) is insoluble in dilute ammonia solution AND in conc. ammonia solution

Question 21

Method of further halide test with AMMONIA

Answer 21

• Add dilute ammonia solution to metal halide solution
• Then add concerntrated ammonia solution

Question 22

Why is ACID added for the HALIDE test?

Answer 22

• To remove any presence of CO3(2-)
• False positive result of a white ppt of Ag2CO3
  would have been formed

Question 23

Why is HNO3 used as an ACID in the HALIDE?

Answer 23

• HCl contains Cl(-)n ions
• False positive of result of a
  white ppt of AgCl
• H2SO4 contains SO4(2-) ions
• False positive of result of a
  white ppt of Ag2SO4

Question 24

Ionic Equation for test for AMMONIUM IONS

Answer 24

NH4+ (aq) + OH- (aq) 🡪 NH3 (g) + H2O (l)