Analysis

Question 1

What are the four flame tests and the results?

Answer 1

Li+ = red
Na+ = Intense yellow
K+ = Lilac
Ca 2+ = Dull orange/brick red

Question 2

How do you identify an Ammonium ion - NH4+ (test, result and equation)?

Answer 2

Test: Add solution/solid to sodium hydroxide solution. Warm the mixture and test any gas given off with damp red litmus paper.

Result: If ammonium ions are present, pungent smelling gas is produced which turns damp red litmus paper blue.

Equation: NH4+ + OH- —> NH3 + H2O

Question 3

How to identify metal cations by using precipitation reactions?

Answer 3

• Metal hydroxides are insoluble so can be precipitated from an aqueous solutions of metals salts by adding sodium hydroxide.
• You add the sodium hydroxide a drop at a time to the precipitate.

Question 4

What are the three metal cations that can be added to sodium hydroxide?

Answer 4

• Copper (ll) ion Cu2+
• Iron(lll) ion Fe3+
• Iron(ll) ion Fe2+

Question 5

What happens when sodium hydroxide is added to a copper(ll) ion?

Answer 5

• Blue precipitate formed

- Cu2+ + 2OH- —> Cu(OH)2

Question 6

What happens when sodium hydroxide is added to a iron(ll) ion?

Answer 6

• Moss green precipitate

- Fe2+ + 2OH- —> Fe(OH)2

Question 7

What happens when sodium hydroxide is added to a iron(lll) ion?

Answer 7

• Foxy red precipitate

- Fe3+ + 3OH—> Fe(OH)3

Question 8

How do you identify halide ions (anions) by precipitation with silver nitrate solution?

Answer 8

You add to an aqueous solution of the solid being tested some dilute nitric acid, followed by a few drops of silver nitrate solution.

Question 9

What are the three halide ions (anions) that precipitate with silver nitrate solution and nitric acid?

Answer 9

• Chloride ion Cl-
• Bromide ion Br-
• Iodide ion I-

Question 10

What happens when silver nitrate solution and nitric acid are added to a chloride ion?

Answer 10

• White precipitate of silver chloride is formed

- Ag+ + Cl- —> AgCl

Question 11

What happens when silver nitrate solution and nitric acid are added to a bromide ion?

Answer 11

• Cream precipitate of silver bromide is formed

- AgBr+ + Br- —> AgBr

Question 12

What happens when silver nitrate solution and nitric acid are added to a iodide ion?

Answer 12

• Yellow precipitate of silver iodide is formed

- Agl+ + I- —> AgI

Question 13

How do you identify sulfate ions - SO4 2- (test, result and equation)?

Answer 13

Test: Add to an aqueous solution of the solid being tested dilute hydrochloric acid followed by a few drops of barium chloride solution.

Result: White precipitate (of barium sulfate)

Equation: Ba2+ + SO4 2- —> BaSO4

Question 14

How do you identify carbonate ions - CO3 2- (test, result and equation)?

Answer 14

Test: Add to either a solid or an aquesous solution of the solid dilute hydrochloric/ nitric acid.

Result: Bubbles/effervescence seen. Limewater turns milky due to carbon dioxide having been given off.

Equation: CO3 -2 + 2H+ —> CO2 + H2O

Question 15

How do you do the flame test?

Answer 15

• Dip nichrome wire in concentrated hydrochloric acid, them into solid.
• Hold in blue bunsen burner flame

Question 15

Why is any acid used?

Answer 15

To get rid of the carbonate and sufite ions before test.

Question 17

What is the test and result for hydrogen?

Answer 17

Test: Place a lighted splint in mouth of test tube.
Result: Speaky pop sound produced

Question 18

What is the test and result for oxygen?

Answer 18

Test: Place glowing splint into mouth of test tube.
Result: Splint relights.

Question 19

What is the test and result for carbon dioxide?

Answer 19

Test: Bubble through limewater.
Result: Limewater turns milky/cloudy.

Question 20

What is the test and result for ammonia?

Answer 20

Test: Damp red litmus paper
Result: Damp litmus paper turns blue

Question 21

What is the test and result for chlorine?

Answer 21

Test: Damp blue litmus paper.
Result: Litmus paper turns red then bleaches (white)