2(c) Gases in the atmosphere Flashcards
composition of air?
- nitrogen (78%)
- oxygen (21%)
- argon (0.9%)
- carbon dioxide (0.04%)
name the practical to determine the approx. percentage of volume of O2 in the air: (metal or non-metal):
- by burning phosphorous in air inside a bell jar
- the oxidation of iron with wet iron fillings
combustion?
the scientific word for burning which all involves a chemical change in which oxygen reacts with elements or compounds to produce oxides
are combustion reactions exo or endo?
exothermic as they give off heat
magnesium combustion (observation)
- intense white flame
- white power produced (magnesium oxide)
equation: 2Mg (s) + O2 (g) –> 2MgO (s)
hydrogen combustion (observation)
- exothermic
- water is produced
equation: 2H2 + O2 –> 2H20
sulfur combustion (observation)
- blue flame
- colourless, poisonous gas produced
thermal decomposition?
a term used to describe reactions where a substance breaks down due to the action of heat
what do carbonates of metals from the lower half of the reactivity series tend to decompose on heating to produce?
the metal oxide and carbon dioxide
metal carbonate –> metal oxide + carbon dioxide
observations from the thermal decomposition of copper (II) carbonate?
it is a green powder and slowly darkens as black copper(II) oxide is produced
- the carbon dioxide given off
equation for the thermal decompostion of copper(II) carbonate?
CuCO3 –> CuO + CO2
what do greenhouse gases do?
- they trap the shortwave radiation form the sun that strikes the Earth’s surface (some is re-emitted; as infrared radiation and some is absorbed from the surface)
examples of greenhouse gases:
- carbon dioxide
- methane
- water vapour
enhanced greenhouse effect?
increasing levels of carbon dioxide, although present in only a small amount, is causing significant upset to the earth’s natural conditions by trapping extra heat energy
