Atoms and Molecules Class 9 Worksheet

1.Give an example of a tri-atomic molecule of an elem ent.
2.Give one word for the following:
(i) Positively charged ion
(ii) A group of atoms carrying a charge
3.What are polyatomic ions? Give examples
4. State the Postulates of Dalton Theory?
5.What is the molecular formula for
i)Calcium hydroxide
ii)Magnesium Phosphate
iii)zinc Nitrate
iv)Aluminium oxide
v)Sodium Carbonate
vi)Aluminium chloride
5). 6.2.42g of copper gave 3.025 g of a black oxide of copper, 6. 4 9 g of a black oxide, on reduction with hydrogen, gave 5.192g of copper. Sho w that these figures are in accordance with law of constant proportion?

7.alculate the number of aluminium ions present in 0.051 g of aluminium oxide. ( Hint: The mass of an ion is the same as that of an atom o f the same element. Atomic mass of Al = 27 u)

8.What is the mass of:
(a) 0.2 mole of oxygen atoms?
(b) 0.5 mole of water molecules?
9.ive the names of the elements present in the f ollowing compounds.
(a) Quick lime
(b) Hydrogen bromide
(c) Baking powder
(d) Potassium sulphate.

10. Which has more number of atoms, 100 grams of so dium or 100 grams of iron (given, atomic mass of Na = 23 u, Fe = 56 u)?

11.alculate the formula unit masses of ZnO, Na₂ O, K ₂ CO ₃ , given atomic masses of Zn = 65 u, Na = 23 u, K = 39 u, C = 12 u, and O = 16 u.
12.State the differences betwee n an atom or a molecule.
13.Calculate the number of moles for the following:
a) 52 g of He
b) 17 g of water