CBSE Class 9 Atoms and molecules:Important Sample paper Questions

Q1.What is meant by Avogadro’s constant?

Q2. Write the formulae of :-

a. Sodium chloride

b. Aluminium oxide

c. Aluminium sulphate

d.Calcium Hydroxide

e.Sodium Carbonate

Q3. Give postulates of Dalton’s atomic theory

.Q4. What is meant by valency of an element?

Q5. Give the names of elements present in:-

a. Potassium sulphate

b. Hydrogen bromide

c. Quick lime

d. Baking powder

Q6. a. Define the term mole.

b. What are polyatomic ions?

Q7. Define following parts:-

a. Molecular mass b. Relative formula mass

c. Isobars d. Cation e. Anion

Q8.What is Atomicity? What is the atomicity of Oxygen,Ozone,Sulphur,and Aluminium Sulphate

Q9. Calculate the mass of 0.5 mole of sugar (C12H22O11) ( Atomic mass of Fe=56u, C=12u,H=1u,O=16u).

Q10. Mention the postulates of Dalton’s atomic theory that explains the law of constant proportions.

b. Write the formulae and names of compounds formed by combination of:-

i) Fe³⁺ and SO₄^2-

ii) NH⁴⁺ and CO₃^2-

Q11. Compute the number of ions present in 5.85 g of sodium chloride.

Q12. In a chemical reaction 5.3 g of sodium carbonate reacted with 6 g of acetic acid then it was observed that 8.2 g of sodium acetate, 0.9 g of water and x g of carbon dioxide were produced. What is the value of x?

Q13.What is Difference Between Formula Unit mas and Molecular Mass.

Calculate the formula unit mass of CaCO3 (given at masses: Ca = 40. 0μ, c=12 0μ, 0 = 16.0μ

Q14. (i) State ‘Law of constant proportions’.

(ii) Taking the example of water, explain the law of constant proportions.

(iii) Which postulate of Daltons’ atomic theory explains this law?

(iv)What were the draw backs of Dalton Atomic Theory

Q15.(i)How many moles are present in 12.044 X 10²³ molecules of Oxygen Gas

(ii)How many sodium atoms are present in 0.69g of Sodium

Q16.Give one example of diatomic triatomic and tetratomic element molecule

Q17. When 3 g of carbon is burnt with 8 gram of oxygen then 11 grams of Carbon dioxide is produced. And when 3 g of carbon is burnt with 50 g of oxygen then what mass of Carbon dioxide gas will be formed.Which law of chemical combination will govern your answer

Q18.What are cations, and give two example of bivalent cations

Q19.Calculate the ratio by number of atoms in Ammonia if Ratio by mass is 14:3

Q21. Calculate the number of oxygen  ions present in 0.051 g ofaluminium oxide

Q22.Find the percentage of water of crystallization in feSO4. 7H2O.

Q23.

. Write the names of the compounds represented by the following formulas:

a) Mg(NO3)2 b) K2SO4 c )Ca3N2