Oxygen and Oxides

Question 1

What percentage of air is made up of oxygen?

Answer 1

Oxygen makes up 21% of the air.

Question 2

How can the proportion of oxygen in air be demonstrated?

Answer 2

By reacting a fixed amount of air with heated copper to form copper(II) oxide.

Question 3

What is the reaction equation for copper reacting with oxygen?

Answer 3

2Cu(s) + O2(g) → 2CuO(s)

Question 4

What happens to the volume of air when copper(II) oxide is formed?

Answer 4

The volume of air decreases, and only 79% of the original volume remains after the reaction.

Question 5

How can oxygen percentage be calculated using phosphorous burning?

Answer 5

Using the formula: % of oxygen = (Volume of oxygen used / Volume of air at start) x 100.

Question 6

What was the calculated percentage of oxygen using the phosphorous method?

Answer 6

% of oxygen = (1 / 5) x 100 = 20%.

Question 7

What is the reaction of magnesium with oxygen?

Answer 7

2Mg(s) + O2(g) → 2MgO(s)

Produces a bright white light and a basic solution with pH 8.

Question 8

What is produced when carbon reacts with oxygen?

Answer 8

C(s) + O2(g) → CO2(g)

Produces a colourless and odourless gas with an acidic solution (pH 6).

Question 9

What is produced when sulfur reacts with oxygen?

Answer 9

S(s) + O2(g) → SO2(g)

Produces a pungent yellowish gas with an acidic solution (pH 1).

Question 10

What do metals form when they react with oxygen?

Answer 10

Metals react with oxygen to form oxides that dissolve in water to form alkalies.

Question 11

What do non-metals form when they react with oxygen?

Answer 11

Non-metals react with oxygen to form oxides that dissolve in water to form acids.