Oxygen and oxides: experiments, lab prep, reactions of oxygen

Question 1

name 4 main components of air

Answer 1

• nitrogen
• oxygen
• argon
• carbon dioxide

Question 2

Percentage of nitrogen in air

Answer 2

78%

Question 3

Percentage of oxygen in air

Answer 3

21%

Question 4

Percentage of argon in air

Answer 4

0.9%

Question 5

Percentage of carbon dioxide in air

Answer 5

0.04%

Question 6

percentage of other gases in air

Answer 6

0.06%

Question 7

what is the name of tube which copper is packed in when determining percentage of oxygen in air?

Answer 7

silica tube

Question 8

how do you determine percentage of oxygen in air using copper?

Answer 8

• set up apparatus with 100cm3 of air in one syringe
• heat copper at one end of silica tube
• pass air over it using syringes so that copper reacts with oxygen
• move bunsen flame along the tube so that it heats fresh copper
• final volume of air will be approx. 79cm3, so therefore copper is 21cm3

Question 9

how do you determinepercentage of oxygen in air using iron filings?

Answer 9

• place wet filings at end of burette placed upside down in trough of water
• over time water rises up
• the volume of oxygen is the difference between initial and end volume

Question 10

why does water rise up the burette when determining percentage of oxygen in air using iron filings?

Answer 10

• iron reacts with oxygen - iron oxide

- water rises to fill up space oxygen took up

Question 11

formula to work out percentage of oxygen

Answer 11

volume of oxygen used
———————————- x 100
volume of air at start

Question 12

describe similar experiment using iron wool

Answer 12

• soak iron wool in acetic acid (acts as catalyst)
• push it up test tube and invert it in trough of water
• measure start and end volume to find percentage of oxygen

Question 13

how to determine percentage of oxygen in air using phosphorus?

Answer 13

• place piece of white phosphorus on water (levels in and out of tube should be same)
• touch phosphorus with hot metal rod and place bung on tube
• phosphorus will burn to form phosphorus oxide
• water level in tube will rise as oxygen is used up

Question 14

How to prepare oxygen in lab

Answer 14

• decomposition of hydrogen peroxide using manganese oxide as catalyst
• collect with syringe or over water

Question 15

why can oxygen be collected over water?

Answer 15

it is insoluble so does not dissolve in water

Question 16

observation of magnesium burning in oxygen

Answer 16

• bright, white flame

- forms white powder

Question 17

observation of carbon burning in oxygen

Answer 17

• orange-yellow flame

- forms colourless gas

Question 18

observation of sulphur burning in oxygen

Answer 18

• blue flame

- forms colourless gas

Question 19

acidity of magnesium oxide

Answer 19

• basic

- forms alkaline solution of magnesium hydroxide

Question 20

acidity of sulphur dioxide

Answer 20

• acidic

- forms acidic solution of sulphurous acid (pH 3-4) - H2SO3

Question 21

acidity of carbon dioxide

Answer 21

• acidic

- forms acidic solution of carbonic acid (pH 5-6) - H2CO3