English Medium इयत्ता ९ - CBSE Question Bank Solutions

Calculate the molecular masses of the following compounds  :

Ethyne, C₂H₂

(Atomic masses : C = 12 u ; H = 1 u)

Calculate the molecular masses of the following compounds :

Ethanol, C₂H₅OH

Which of the following elements has the same molecular mass as its atomic mass ?

Calculate the formula masses of the following compounds :

Sodium oxide, Na₂O

Calculate the formula masses of the following compounds :

Calcium carbonate

Calculate the formula masses of the following compounds :

1. Calcium chloride
2. Sodium carbonate

(Given : Atomic masses : Ca = 40 u ; Cl = 35.5 u ; Na = 23 u ; C = 12 u; O = 16 u)

How many molecules are present in one gram molecular mass of a substance ?

Convert 12 g of oxygen gas into moles.

Calculate the mass of 12.044 × 1025 molecules of oxygen (O2).

How many moles are there in 34.5 g of sodium ? (Atomic mass of Na = 23 u)

Define gram molecular mass of a substance. How much is the gram molecular mass of oxygen ?

If sulphur exists as S₈ molecules, calculate the number of moles in 100 g of sulphur. (S = 32 u)

What is meant by the ‘molar mass’ of a substance ? State the unit in which molar mass is usually expressed.

Calculate the molar masses of the following substances. Write the results with proper units.

1. Ozone molecule, O3
2. Ethanoic acid, CH3COOH

The mass of one molecule of a substance is 4.65 × 10–23 g. What is its molecular mass ? What could this substance be ?

The mass of one steel screw is 4.11g. Find the mass of one mole of these steel screws. Compare this value with the mass of the Earth (5.98 × 10²⁴kg). Which one of the two is heavier and by how many times?

What is the SI prefix for each of the following multiples and submultiples of a unit?

1. 10³
2. 10^–1
3. 10^–2
4. 10^–6
5. 10^–9
6. 10^–12

What are ionic and molecular compounds? Give examples.