English Medium कक्षा ९ - CBSE Question Bank Solutions

Play a game for writing formula.

Example 1: Make placards with symbols and valencies of the elements separately. Each student should hold two placards, one with the symbol in the right hand and the other with the valency in the left hand. Keeping the symbols in place, students should criss-cross their valencies to form the formula of a compound.

Play a game for writing formula.

Example 2: A low-cost model for writing formulae: Take empty blister packs of medicines. Cut them in groups according to the valency of the element, as shown in the figure. Now, you can make formulae by fixing one type of ion into other.

For example:

The formula for sodium sulphate:

2 sodium ions can be fixed on one sulphate ion.

Hence, the formula will be Na₂SO₄.

Do it yourself:

Now, write the formula of sodium phosphate.

Calculate the molecular mass of H₂.

Calculate the molecular mass of O₂.

Calculate the molecular mass of Cl₂.

Calculate the molecular mass of CO₂.

Calculate the molecular mass of CH₄.

Calculate the molecular mass of C₂H₆.

Calculate the molecular mass of C₂H₄.

Calculate the molecular mass of NH_3.

Calculate the molecular mass of CH₃OH.

Calculate the formula unit mass of ZnO given the atomic mass of:

• Zn = 65 u
• Na = 23 u
• K = 39 u
• C = 12 u
• O = 16 u

Calculate the formula unit mass of Na₂O given the atomic mass of

• Zn = 65 u
• Na = 23 u
• K = 39 u
• C = 12 u
• O = 16 u

Calculate the formula unit mass of K₂CO₃ given the atomic mass of

• Zn = 65 u
• Na = 23 u
• K = 39 u
• C = 12 u
• O = 16 u

What are the different states in which water is found during the water cycle?

What are the desirable characters of bee varieties suitable for honey production?

What is pasturage and how is it related to honey production?

For increasing production, what is common in poultry, fisheries and bee-keeping?

Write advantages of bee keeping.

How bee colony works? What values can be seen in the organisation of bee colony?