NCERT Class 9 Science Solutions: Chapter 3 –Atoms and Molecules Part 4

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Question 5:

Q. Give the names if the elements present in the following compounds:

(a) Quick lime

(b)Hydrogen bromide

(c) Baking powder

(d) Potassium sulphate

A.

Image Showing Compound,Its Chemical Formula and Its Elements
Image showing compound,its chemical formula and its elements.

Compound

Chemical formula

Elements present

Quick lime

Calcium, oxygen

Hydrogen bromide

Hydrogen, bromine

Baking powder

Sodium, hydrogen, carbon, oxygen

Potassium sulphate

Potassium, Sulphur, Oxygen

Question 6:

Q. Calculate the molar mass of the following substances:

(a) Ethyne,

Image of Ethyne for Atom and Molecules

Image of Ethyne for Atom and Molecules

A. Molar mass of Ethyne,

(b)Sulphur molecule,

A. Molar mass of Sulphur molecule,

(c) Phosphorus molecule, (atomic mass of phosphorus=31)

A. Molar mass of phosphorus molecule,

(d) Hydrochloric acid, HCl

A. Molar mass of hydrochloric acid,

(e)Nitric acid,

A. Molar mass of Nitric acid, =

Question 7:

Q. what is the mass of - -

(a) 1 mole of nitrogen atoms?

A. The mass of 1 mole of nitrogen atoms is.

(b) 4 moles of Aluminium atoms (Atomic mass of Aluminium =27)?

A. The mass of 4 moles of Aluminium atoms is

(c) 10 moles of sodium sulphite ?

A. The mass of 10 moles of sodium sulphite is

Question 8:

Q. Convert into mole.

(a) 12 g of oxygen gas

A. 32 g of oxygen gas

Then, 12 g of oxygen gas

(b) 20 g of water

A. 18 g of water

Then, 20 g of water

(c) 22 g of carbon dioxide

A. 44 g of carbon dioxide

Then, 22 g of carbon dioxide

Question 9:

Q. What is the mass of?

(a) 0.2 mole of oxygen atoms?

A. Mass of one mole of oxygen atoms

Then, mass of 0.2 mole of oxygen atoms

(b) 0.5 mole of water molecules?

A. Mass of one mole of water molecule

Then, mass of 0.5 mole of water molecules

Question 10:

Q. Calculate the number of molecules of sulphur present in 16 g of solid sulphur.

Image of Sulphur for Atom and Molecules

Image of Sulphur for Atom and Molecules

A. 1 mole of solid sulphur

i.e., 256 g of solid sulphur contains

Then, 16 g of solid sulphur contains

Question 11:

Q. Calculate the number of Aluminium icons present in 0.051 g of Aluminium oxide.

(Hint: The mass of an ion is the same as that of an atom of the same element. Atomic mass of

A. 1 mole of Aluminium oxide

i.e.,

Then, 0.051 g of

The number of Aluminium ions present in one molecule of Aluminium oxide is

2. Therefore, the number of Aluminium icons present in molecules of Aluminium oxide

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