3.4 Atmosphere and Acids

Question 1

What colour is methyl orange in acid?

Answer 1

Red

Question 2

What colour is methyl orange in neutral?

Answer 2

Yellow

Question 3

What colour is methyl orange in alkali?

Answer 3

Yellow

Question 4

What colour is phenolphthalein in acid?

Answer 4

Colourless

Question 5

What colour is phenolphthalein in neutral?

Answer 5

Colourless

Question 6

What colour is phenolphthalein in alkali?

Answer 6

Pink

Question 7

What colour is red litmus in acid?

Answer 7

Red

Question 8

What colour is red litmus in neutral?

Answer 8

Red

Question 9

What colour is red litmus in alkali?

Answer 9

Blue

Question 10

What colour is blue litmus in acid?

Answer 10

Red

Question 11

What colour is blue litmus in neutral?

Answer 11

Blue

Question 12

What colour is blue litmus in alkali?

Answer 12

Blue

Question 13

What is air composed of?

Answer 13

Nitrogen, Oxygen, Argon, Carbon Dioxide

Question 14

What percentage of Nitrogen is in the air?

Answer 14

78%

Question 15

What percentage of Oxygen is in the air?

Answer 15

21%

Question 16

What percentage of Argon is in the air?

Answer 16

0.96%

Question 17

What percentage of Carbon Dioxide is in the air?

Answer 17

0.04%

Question 18

What is element combustion?

Answer 18

Element + Oxygen —–> Element Oxide

Question 19

What observations are made when magnesium reacts with oxygen?

Answer 19

• Bright white light
• White powder formed

Question 20

What observations are made when sulphur reacts with oxygen?

Answer 20

• Blue flame

Question 21

What observations are made when hydrogen reacts with oxygen?

Answer 21

• Squeaky pop

Question 22

What does the chemical test for oxygen show?

Answer 22

Glowing splint relighting

Question 23

Define acid

Answer 23

H+ donor

Question 24

Define alkali

Answer 24

OH- donor

Question 25

Define base

Answer 25

H+ acceptor

Question 26

What is the acid + base reaction?

Answer 26

Acid + Base -----> Salt + Water

Question 27

What is the acid + carbonate reaction?

Answer 27

Acid + Carbonate -----> Salt + Water + Carbon Dioxide

Question 28

What are observations of an acid + carbonate reaction?

Answer 28

- Carbonate disappears (used up in reaction) - Fizzing (carbon dioxide produced)

Question 29

How to find the percentage of oxygen in original air?

Answer 29

21cm3/ 100cm3 X 100 = 21%

Question 30

What is the chemical test for oxygen?

Answer 30

Glowing splint --> Relights

Question 31

What type of solution do metal oxides form?

Answer 31

Alkaline solutions

Question 32

What type of solution do non-metal dioxides form?

Answer 32

Acidic solutions

Question 33

How can we determine whether an unknown element is a metal or a non-metal?

Answer 33

1) Combust it in oxygen 2) Dissolve the oxide formed 3) Check the pH of the solution with. an indicator

Question 34

What is an acid?

Answer 34

An H+ donor

Question 35

What is a base?

Answer 35

An H+ acceptor

Question 36

What is an alkali?

Answer 36

An OH- donor

Question 37

What are important bases?

Answer 37

Ammonia (NH3) All metal oxides All metal hydroxides

Question 38

What are important acids?

Answer 38

Hydrochloric acid (HCl) Nitric acid (HNO3) Sulphuric acid (H2SO4) Phosphoric acid (H3PO4) Carbonic acid (H2CO3)

Question 39

What are important alkali?

Answer 39

Sodium hydroxide (NaOH) Potassium hydroxide (KOH) Ammonium hydroxide (NH4OH) All soluble metal hydroxides

Question 40

What is a polyatomic ion?

Answer 40

An ion that contains more than one atom

Question 41

What is produced when a base reacts with water?

Answer 41

Salt + Water

Question 42

What is one important observation in an acid + base reaction?

Answer 42

The base disappears (used up in the reaction)

Question 43

How to carry out an acid-alkali titration?

Answer 43

1) Use a volumetric pipette to place 25cm3 of the unknown alkali into a conical flask 2) Add a few drops of methyl orange or phenolphthalein indicator into the flask 3) Fill burette with known acid and clamp it above the flask 4) Measure the initial volume of the known acid on the burette to the nearest 0.05cm3 5) Use the burette to add acid into the conical flask drop-by-drop, swirling the flask 6) Close burette tap as soon as the colour in the conical flask changes (will be alkali colour or acidic colour) 7) Measure the final volume of known acid on the burette to the nearest 0.05cm3 8) Calculate titre (final volume - initial volume) 9) Repeat for concordant (within 0.2cm3) titres