Oxygen and Oxides

Question 1

what are the four gases in our air?

Answer 1

• nitrogen 78%
• oxygen 21%
• argon 0.96%
• carbon dioxide 0.04%

Question 2

how can you measure the percentage of oxygen?

Answer 2

• react it with another element, often a metal
• heat the metal
• the air gradually decreases in volume until all of the oxygen has been added to the metal

Question 3

why would the air in an oxygen percentage experiment not decrease by 21%?

Answer 3

• the metal wasn’t heated for long enough for all the oxygen to be reacted
• there’s a leak in the apparatus

Question 4

what is element combustion?

Answer 4

element combustion is when an element reacts with oxygen to produce an oxide

Question 5

what is the word equation for element combustion?

Answer 5

element + oxygen -> element oxide

Question 6

oxide name if the element was a metal?

Answer 6

metal oxide (state = solid)

Question 7

oxide name if element was a non-metal?

Answer 7

non-metal dioxide (state = gas)

Question 8

magnesium combustion word + symbol equation?

Answer 8

magnesium + oxygen -> magnesium oxide
2Mg(s) + O2(g) -> 2MgO(s)

Question 9

observations of magnesium combustion?

Answer 9

• bright white light
• white powder formed

Question 10

sulphur combustion word + symbol equation?

Answer 10

sulphur + oxygen -> sulphur dioxide
S(s) + O2(g) -> SO2(g)

Question 11

observations of sulphur combustion?

Answer 11

• blue flame

Question 12

hydrogen combustion word + symbol equation?

Answer 12

hydrogen + oxygen -> water
2H2(g) + O2(g) -> 2H2O(l)

Question 13

observations of hydrogen combustion?

Answer 13

• squeaky pop

Question 14

symbol for iron(II) ion?

Answer 14

Fe2+

Question 15

symbol for iron(III) ion?

Answer 15

Fe3+

Question 16

symbol for copper ion?

Answer 16

Cu2+

Question 17

symbol for silver ion?

Answer 17

Ag+

Question 18

symbol for zinc ion?

Answer 18

Zn2+

Question 19

symbol for lead ion?

Answer 19

Pb2+

Question 20

chemical test for oxygen?

Answer 20

glowing splint -> relights
- this is because the oxygen allows the wood in the splint to combust more efficiently

Question 21

what happens if oxides dissolve in water?

Answer 21

• they tend to form an acidic or alkaline solution

Question 22

what solutions do metal oxides form?

Answer 22

alkaline (pH 8-14)

Question 23

what solutions do non-metal dioxides form?

Answer 23

acidic (pH 0-6)

Question 24

how to determine whether an unknown element was a metal or non-metal?

Answer 24

• combust it in oxygen
• dissolve the oxide formed
• check the pH of the solution with an indicator