4. Write the chemical formulae of the following

Atoms and Molecules class 9

4. Write the chemical formulae of the following.

(a) Magnesium chloride
(b) Calcium oxide
(c) Copper nitrate
(d) Aluminium chloride
(e) Calcium carbonate.

Answer:

The chemical formula of a compound balances the valance electrons. Magnesium has two valence electron while one chlorine atom needs one electron in its outer shell.

 

a) MgCl_2, b) CaO, c) Cu(NO₃)_2, d) AlCl_3, e) CaCO₃

5. Give the names of the elements present in the following compounds.
(a) Quick lime
(b) Hydrogen bromide
(c) Baking powder
(d) Potassium Sulphate.

Answer:

a) Quick lime has a chemical formula of CaO. So, elements present in quick lime are calcium and oxygen.

b) Hydrogen bromide: HBr, Elements present here are hydrogen and bromine.

c) Baking powder is Sodium hydrogen carbonate (NaHCO₃), so it contains sodium, hydrogen, carbon and oxygen element.

d) Potassium sulphate: (K₂SO₄). Here elements present are potassium, sulphur and oxygen.

Next: Question 6: calculation of molar mass.

See also: Question3. What are polyatomic ions? Give examples.