1. Nitrogen constitutes nearly __ % of the atmosphere.   57   79   42   21   Hint Half-n-half Clue   2. A space that contains no air or any gas is known as   Vacuum   Bubble   Hollow   Pressurized Cabin   Half-n-half Clue   3. Carbon dioxide is lighter than air.   True   False   4. Which of the following is NOT a noble gas?   Argon   Krypton   Hydrogen   Helium   Half-n-half Clue   5. Air is   An Alloy   A Compound   A Mixture   An Element   Half-n-half Clue   6. What gas is evolved when HCl is poured on marble chips?   Calcium Carbonate   Hydrogen   Carbon Dioxide   Hydrogen Peroxide   Half-n-half Clue   7. Air is a   Gas   Liquid   Solid   Plasma   Half-n-half Clue