Class 9 Atoms and Molecules Important Questions

Important Questions Notes NCERT Solutions MCQ Quiz – 1 MCQ Quiz – 2

1. When 3.0 g of carbon is burnt in 8.00 g oxygen, 11.00 g of carbon dioxide is produced. What mass of carbon dioxide will be formed when 6.00 g of carbon is burnt in 50.00 g of oxygen? Which law of chemical combination will govern your answer?
2. What is the mass of:
   1. 0.2 mole of oxygen atoms?
   2. 0.5 mole of water molecules?
   3. 3.011 x 10²³ number of N atoms?
3. Which postulate of Dalton’s atomic theory is the result of the law of conservation of mass?
4. Calculate the number of aluminium and oxygen ions present in 0.051 g of aluminium oxide ?
5. Write the formula of :
   1. Calcium hydride
   2. Ammonium hydroxide
   3. Zinc sulphite
   4. sulphur dioxide
   5. calcium hydrogen carbonate
6. A gold sample contains 90% of gold and rest of cpper. How many atoms of gold are present in one gram of this sample of gold.
7. An element X of valency 3 combines with another element Y of valency 2. What will be the formula of the compound formed.
8. Calculate the number of ions present in 5.85 g of sodium chloride.
9. How many moles of calcium carbonate are present in 10 g of the substance?
10. Calculate the mass of 3.011 x 10²⁴ atoms of carbon.