Question

I need your help.....

I will be writing an entrance exam and the syllabus includes even the concept of mole.....

1. Explain the concept of mole?

2. Calculations based on weight-weight ....

3. Weight-volume and Volume-volume relationship......

Also please help me out in getting some sample entrance exam papers........

Thanking you

Gauthami

Answer 1

You are not supposed to ask multiple questions, please upload each qns independently.
However I'm solving the first question.

In chemistry, the term mole represents a pile or mass of atoms, molecules, ions or electrons. Just as common man measures quantity in terms of kilograms or dozens, a chemical scientist deals with a 'mole' of atoms, molecules, ions or electrons.

Mole is defined as the amount of a substance, which contains the same number of chemical units (atoms, molecules, ions or electrons) as there are atoms in exactly 12 grams of pure carbon-12. A mole represents a collection of 6.023 x 1023 ( Avogadro's number) chemical units. Thus a mole represents the quantity of material, which contains one Avogadro's number of chemical units of any substance. The unit of mole is denoted as 'mol'.

For example

One mole of hydrogen atoms = 6.023 x 1023 atoms of hydrogen

One mole of hydrogen molecules = 6.023 x 1023 molecule of hydrogen

One mole of electrons = 6.023 x 1023 electrons

One mole of sodium ions (Na+) = 6.023 x 1023Na+ ions

It can be thus concluded that,

One mole of atoms = 6.023 x 1023 atoms = Gram atomic mass of the element.

One mole of molecules = 6.023 x 1023 molecules = Gram molecular mass.