Elements and compounds Flashcards
Define an element
A substance containing only one type of atom
Define a compound
A substance containing two or more different types of atoms chemically bonded together
Write the chemical equation for the decomposition of H2O2
2H2O2 –> 2H2O + O2
What is a molecule?
When two or more atoms are chemically bonded together
What is the word equation for the decomposition of hydrogen peroxide
hydrogen peroxide –> water + oxygen
How can you prepare oxygen in the lab?
- Add hydrogen peroxide (H2O2) to a conical flask.
- Connect a bung with tubing to the top of the conical flask.
- Fill a trough with water
- Submerge two or three test tube in the water removing all the air from them
- Arrange each of them upside down filled with water- ready to bubble oxygen into them
- Remove the bung and add a small spatula of manganese dioxide (catalyst) and quickly replace the bung.
- Allow a small amount of bubbles to escape before you start collecting the pure oxygen by down ward displacement.
What type of reaction is this?
2H2O2 –> 2H2O + O2
decomposition
A –> B + C
What would you observe during the decomposition of hydrogen peroxide using the catalyst manganese dioxide?
Fizzing
manganese dioxide is not used up
What is the name of the method used to collect oxygen druring the decomposition of hydrogen peroxide?
Downward displacement of water
What is the test for oxygen?
glowing splint
relights
How can you make carbon dioxide in a lab?
- Add a sample of CuCO3 in a test tube.
- Add a bung and delivery tube to the end of the test tube
- Collect the carbon dioxide by upward displacement of air by placing the delivery tube into an upright test tube.
NOTE: CO2 is more dense than air and will fill the test tube- pushing the air out.
What is the test for carbon dioxide?
bubble through limewater
limewater turns cloudy
Write the word equation for the reaction thermal decomposition of copper (II) carbonate
copper (II) carbonate –> copper oxide + carbon dioxide
Write the word equation for the combustion of magnesium.
combustion means reaction with oxygen
magnesium + oxygen –> magnesium oxide
What is the chemical equation for the thermal decomposition of copper (II) carbonate?
CuCO3 –> CuO + CO2
What type of reaction is this?
2Ba + O2 –> 2BaO
reaction with oxygen so it is called combustion or oxidation
Why can’t we collect carbon dioxide by downward displacement of water?
Carbon dioxide is soluble in water- some of it will dissolve in the water
What would you observe when you burn magnesium in oxygen?
grey solid turns to a white powder
very bright light
How can we collect the gas carbon dioxide?
Upward displacement of air
CO2 is more dense than air and will fill an upright test tube- pushing (displacing) the air up and out.
Is this reaction endothermic or exothermic?
Magnsium + oxygen –> magnesium oxide
exothermic - both heat and light are given off
Write the word equation for the combustion of sulfur
sulphur + oxygen –> sulfur dioxide
What would you observe if you plunge a metal oxide into water with a few drops of universal indicator?
The indicator will turn blue as metal oxides are alkaline
Write the chemical equation for the combusiton of sulfur
S + O2 –> SO2
What would you observe if a non-metal oxide were added to water with a few drops of universal indicator?
It would turn red
non-metal oxide in water forms an acid
H+ ions are present
When sulfur burns in oxygen, what is the colour of the flame?
blue
What are the three oxides which form in a car engine?
sulfur in fuel form sulfur dioxide
nitrogen in air forms nitrous oxide
carbon in fuel form carbon dioxide
These all cause the rain to be acidic -acid rain
What is the most abundance substance in air after nitrogen and oxygen?
argon
List two gases which contribute to the greenhouse effect
carbon dioxide is a green house gas
so is methane!!
What is the percentage of nitrogen in air?
78%
What is the percentage of oxygen in air?
21%