Chemical tests

Question 1

tests for anions and cations produce 5 gases

Answer 1

• ammonia
• carbon dioxide
• oxygen
• chlorine
• hydrogen

Question 2

ammonia turns damp red litmus paper what colour

Answer 2

blue

Question 3

how to test for ammonia

Answer 3

have a test tube with the solution over a bunsen burner

hold litmus paper at the tip of the test tube but don’t touch the sides

the red litmus paper should turn blue

Question 4

what is the reaction for the test for carbon dioxide

Answer 4

limewater turns cloudy

Question 5

test for carbon dioxide

Answer 5

The test for carbon dioxide involves bubbling the gas through an aqueous solution of limewater

Question 6

test for chlorine gas

Answer 6

• handle in a fume cupboard as it is toxic
• put some damp blue litmus paper to the test tube and it should turn red and then bleach white

Question 7

why does damp blue litmus paper turn red at the beginning for chlorine

Answer 7

as acids are produced when chlorine comes into contact with water

Question 8

chlorine has a sharp characteristic, what is it

Answer 8

the smell

Question 9

colour change for chlorine

Answer 9

from damp blue litmus paper to red and then to white

Question 10

Test for hydrogen gas

Answer 10

consists of holding a burning splint at the open end of a test tube of gas

If the gas is hydrogen it burns with a loud “squeaky pop”

Be sure not to insert the splint right into the tube, just at the mouth, as the gas needs air to burn

Question 11

why is there a squeaky pop for hydrogen

Answer 11

its the result of the rapid combustion of hydrogen with oxygen to produce water

Question 12

test for oxygen

Answer 12

place a glowing splint inside a test tube of gas

If the gas is oxygen, the splint will relight

Question 13

how do you tell the test for hydrogen and oxygen apart

Answer 13

Try to remember that a ligHted splint has an H for Hydrogen, while a glOwing splint has an O for Oxygen.

Question 14

how do you carry out a flame test

Answer 14

• dip the loop of a wire in dilute hydrochloric acid
• then place it into a blue flame which decontaminates it
• then place it in a solid sample containing metal ions
• place it back into a blue flame
  a colour change should appear

Question 15

lithium ions produce what colour flame

Answer 15

RED

Question 16

Potassium ions produce what colour flame

Answer 16

LILAC

Question 17

Sodium ions produce what colour flame

Answer 17

YELLOW

Question 18

Copper ions produce what colour flame

Answer 18

Blue- green

Question 19

Calcium ions produce what colour flames

Answer 19

orange- red

Question 20

Metal cations in aqueous solution can be identified by what

Answer 20

the colour of the precipitate they form on addition of sodium hydroxide

Question 21

the metal ion copper forms what precipitate when adding Sodium hydroxide

Answer 21

light blue precipitate formed

Question 22

the metal ion Iron II forms what precipitate when adding Sodium hydroxide

Answer 22

Green precipitate formed

Question 23

the metal ion Iron III forms what precipitate when adding Sodium hydroxide

Answer 23

brown precipitate formed

Question 24

effect of adding sodium hydroxide
to ammonium

Answer 24

Ammonia gas is produced which turns damp red litmus paper blue

Question 25

anions are what

Answer 25

negatively charged ions

Question 26

carbonate contains what ions

Answer 26

CO₃²⁻

Question 27

what is the test for carbonate ions ( anion)

Answer 27

• add dilute hydrochloric acid
• bubble carbon dioxide gas through limewater
• if carbonate ions are present then limewater will turn cloudy and effervescence will happen

Question 28

sulfates contain

Answer 28

SO₄²⁻

Question 29

test for sulfate ions (anion)

Answer 29

• add dilute nitric acid to a test tube
• add aqueous barium nitrate
• a white precipitate should form ( of barium sulphate)

Question 30

halide ions are

Answer 30

ions formed by group 7 elements when they gain an electron

Question 31

halide ions include

Answer 31

Chloride
Bromide
Iodide

Question 32

test for halide ions ( Anion)

Answer 32

• add dilute nitric acid
• add silver nitrate solution
• different precipitates should form of the silver halide

Question 33

what precipitate would silver chloride form for the halide ion test

Answer 33

white

Question 34

what precipitate would silver bromide form for the halide ion test

Answer 34

cream

Question 35

what precipitate would silver iodide form for the halide ion test

Answer 35

yellow

Question 36

water can be identified using 2 tests, what are they

Answer 36

a physical one and a chemical one

Question 37

chemical test for water

Answer 37

Anhydrous copper(II) sulfate turns from white to blue on the addition of water

Question 38

physical test for water

Answer 38

check its boiling point

A sample of the liquid is placed in a suitable container such as a boiling tube and gently heated

Using a thermometer, you can check if the boiling point is exactly 100 oC

Any impurities present will usually tend to raise the boiling point and depress the melting point of pure substance