Gases in the air - Lab production of oxygen Flashcards
What was the first way that someone discovered oxygen?
When mercury is burnt in air, it leaves behind a red ash-like solid substance. Joseph Priestley used a magnifying glass to heat this mercury ash to see if anything would happen. He found that gas was given off. He collected the gas and found that a burning splint would burn very brightly in it.
What is the modern name we would give to the mercury red ash-like solid substance?
Mercury oxide
Name the two original elements in the mercury red ash-like solid substance, a silvery liquid and a colourless gas.
silvery liquid - Mercury
colourless gas - Oxygen
What is the name we give to a reaction where a substance breaks down by the action of the heat?
Thermal decomposition
What was the second experiment?
He heated mercury in a flask until it formed a red powder. The volume of the air in the flask decreased. Antoine Lavoisier did some careful measurements and he found that the red powder had the same mass as the original mercury plus the mass of the air that had been used up. He then heated the red powder and found that he got back exactly the same amount of gas that had been used up before. Lavoisier called this the gas oxygen. His experiment made him believe that when things burnt, they
were combining oxygen in the air.
Name the red powder
Mercury oxide
Write the word equation to show what happened when Lavoisier heated mercury
Mercury + oxygen —–> mercury oxide
Write the word equation to show what happened when Lavoisier heated the red powder
Mercury oxide ( + heat ) —–> oxygen + mercury
What is the test for oxygen gas?
relights a glowing splint
Think of uses and reactions of oxygen
- O2 is taken in during respiration
- O2 produced in photosynthesis
- Oxidation
- Combustion
Oxygen can be produced in the laboratory by the catalytic decomposition of hydrogen peroxide. Write out the word and symbol equation for this.
Word equation : hydrogen peroxide ——-> oxygen + water
Symbol equation : 2 H2O2 ——-> O2 + 2 H2O
Why is a catalyst needed for this reaction?
To speed up a chemical reaction without being used up
Describe oxygen gas
Colourless, odourless gas [ quite reactive ]
The nature of oxygen gas is?
a diatomic molecule [ diatomic - 2 atoms ]
What are the steps of the demo for “Collection of oxygen”
- Wear a lab coat and safety goggles, have your hair tied up.
- Set up a Bunsen burner and add a tiny amount of manganese(IV) oxide to about 2 cm of hydrogen peroxide in a test tube.
- Place your thumb over the test tube to trap the that. Now light a splint and then blow it out ad make sure it is still glowing.
- Place the glowing splint into the neck of the test tube and if the glowing splint relights, then you have created oxygen.
