Gases in Reactions

Question 1

what happens when an element is burnt in air?

Answer 1

it reacts with the oxygen to form an oxide - these oxides can have either acidic or basic character

Question 2

magnesium reaction with oxygen and chemical formula

Answer 2

• magnesium burns with a bright white flame in air and the white powder that is formed is magnesium oxide
• magnesium oxide is slightly alkaline when its dissolved in water

2Mg(s) + O2(g) -> 2MgO(s)

Question 3

hydrogen reaction with oxygen and chemical formula

Answer 3

• hydrogen burns very easily in oxygen - it can be explosive
• it has an almost invisible pale blue flame, and the only product is water as water vapour
• the combustion of hydrogen is often used as a test for hydrogen gas (squeaky pop)
  NOTE: impurities in the air can cause hydrogen to burn with a yellow flame

2H2(g) + O2(g) -> 2H2O(g)

Question 4

sulfur reaction with oxygen and chemical formula

Answer 4

• sulfur burns in air or oxygen with a pale blue flame and produces sulfur dioxide
• sulfur dioxide is acidic when its dissolved in water

S(s) + O2(g) -> SO2(g)

Question 5

what does the thermal decomposition of metal carbonate produce?

Answer 5

carbon dioxide and a metal oxide

Question 6

what is copper(II) carbonate and what does it decompose into?

Answer 6

• a green powder
• will decompose to form carbon dioxide and copper(II) oxide when heated

CuCO3(s) -> CuO(s) + CO2(g)

Question 7

how do you do the copper(II) carbonate experiment?

Answer 7

• heat copper(II) carbonate then collect the gas that’s given off in a test tube
• as carbon dioxide is denser than air, it sinks to the bottom of the tube and can be collected