1. Nitrogen constitutes nearly __ % of the atmosphere.   42   79   57   21   Hint Half-n-half Clue   2. Which of the following is necessary for a substance to burn?   Light   Oxygen   Gasoline   Hydrogen   Half-n-half Clue   3. The atmosphere exerts pressure on the surface of the earth.   True   False   4. When we breathe which of the following gases do we use?   Oxygen   Hydrogen   Carbon Dioxide   Helium   Half-n-half Clue   5. When hydrogen peroxide acts on Manganese Dioxide, oxygen is produced.   True   False   6. Lime water turns milky after carbon dioxide is passed through it.   True   False   7. What gas is evolved when HCl is poured on marble chips?   Hydrogen   Carbon Dioxide   Hydrogen Peroxide   Calcium Carbonate   Half-n-half Clue