3.4.2 Oxygen and Oxides Flashcards
What is the percentage of nitrogen in the air?
78%
What is the percentage of oxygen in the air?
21%
What is the percentage of argon in the air?
0.96%
What is the percentage of carbon dioxide in the air?
0.04%
How to measure percentage oxygen in the air?
React all the oxygen with a metal, and see how much the air shrinks by, for example:
Heat copper oxide in a gas syringe and measure the change in volume in the air. This is how much oxygen in that bit of air. Divide this by the starting amount and multiply by 100 to get the percentage.
If the air in the percentage oxygen experiment didn’t decrease by 21%, what could be the reasons?
- The metal wasn’t heated long enough for all the oxygen to be reacted.
- There was a leak in the apparatus.
What is the general equation for element combustion?
Element + Oxygen –> Element oxide
What is the general name and state of element combustion if the element was a metal?
Metal Oxide — solid
What is the general name and state of element combustion if the element was a non-metal?
Non-metal Dioxide — gas
What is the balanced equation for the combustion of magnesium?
2Mg(s) + O2(g) → 2MgO(s)
What are the observations of magnesium combustion?
Bright white light and white powder formed.
What is the balanced equation for the combustion of sulphur?
S(s) + O2(g) → SO2(g)
What are the observations of sulphur combustion?
Blue flame.
What is the balanced equation for the combustion of hydrogen?
2H2(g) + O2(g) → 2H2O(l)
What are the observations of hydrogen combustion?
Squeaky pop