Flame Tests & Metal Hydroxides

Question 1

What are flame tests used for?

Answer 1

Indicate the presence of certain metal ions

Question 2

How do you conduct a flame test?

Answer 2

Dip a clean wire loop into a sample of the compound being tested, then place the loop into the edge of a blue flame from a Bunsen burner

Question 3

What colour do lithium ions turn the flame? (Li+)

Answer 3

Red

Question 4

What colour do sodium ions turn the flame? (Na+)

Answer 4

Yellow

Question 5

What colour do potassium ions turn the flame? (K+)

Answer 5

Lilac

Question 6

What colour do calcium ions turn the flame? (Ca2+)

Answer 6

Orange-red

Question 7

What colour do copper ions turn the flame? (Cu2+)

Answer 7

Blue-green

Question 8

What is an ion?

Answer 8

Electrically charged particle, formed when an atom or molecule gains or loses electrons

Question 9

What does adding dilute sodium hydroxide (NaOH) identify

Answer 9

certain positive ions in solution (cations)

Question 10

What coloured precipitate do copper ions produce? (Cu2+)

Answer 10

Blue precipitate

Question 11

What coloured precipitate do iron (|||) ions produce? (Fe3+)

Answer 11

Brown precipitate

Question 12

What coloured precipitate do iron (||) ions produce? (Fe2+)

Answer 12

Green precipitate

Question 13

Which ions produce a white precipitate?

Answer 13

Aluminium (Al3+), calcium (Ca2+), magnesium (Mg2+)

Question 14

What happens when you add excess sodium hydroxide to aluminium hydroxide?

Answer 14

Redissolves

Question 15

What happens when NaOH is warmed with ammonium ions (NH4+)

Answer 15

ammonia gas is produced, which is alkaline so it turns damp red litmus paper blue.

Question 16

What is a precipitate?

Answer 16

A suspension of particles in a liquid formed when a dissolved substance reacts to form an insoluble substance

Question 17

What happens when there is a mixture of metal ions in a flame test?

Answer 17

One ion will mask the other

Question 18

Test for carbonates

Answer 18

Carbonates react with dilute acids to form carbon dioxide gas. Carbon dioxide can be identified with limewater.

Question 19

Test for halides

Answer 19

Halide ions in solution produce precipitates with silver nitrate solution in the presence of dilute nitric acid. Silver chloride is white, silver bromide is cream and silver iodide is yellow.

Question 20

Test for sulfates

Answer 20

Sulfate ions in solution produce a white precipitate with barium chloride solution in the presence of dilute HCI.

Question 21

What are instrumental methods

Answer 21

Instrumental methods are accurate, sensitive and rapid.

Question 22

What is flame emission spectroscopy

Answer 22

Flame emission spectroscopy is an example of an instrumental method used to analyse metal ions in solutions.
The sample is put into a flame and the light given out is passed through a spectroscope. The output is a line spectrum that can be analysed to identify the metal ions in the solution and measure their concentrations.

Question 23

What is the ionic equation for metal ions with sodium hydroxide solution?

Answer 23

Cu2+(aq) + 2OH-(aq) → Cu(OH)2(s)

Change to 3+, 3, 3 for a 3+ metal ion
Change Cu to the element you are using