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Dalton's Atomic Theory

Why was mole ...

Question

Why was mole concept introduced in writing a chemical reaction equation? Does the number of grams differ from one mole to another mole?
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Solution

Explanation :1.5 Marks
Reason out: 1.5 Marks

A chemical reaction equation indicates the number of atoms or molecules directly taking part in the reaction. Therefore, it is more convenient to refer to the quantity of a substance in terms of the number of its molecules or atoms, rather than their masses. So, the mole concept was introduced.
Yes, the number of grams in a mole differs from one substance to another substance.

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Why was mole concept introduced in writing the equations of a chemical reaction? [3 MARKS]

According to Avogadro's number, why there is one mole in 12 grams of oxygen? And why not in 8 grams or another amount of oxygen?

Q. Chemical Make up of One of Chloroform

Element	Number of Moles	Mass per Mole (grams)
Carbon	1	12.011
Hydrogen	1	1.008
Chlorine	3	35.453

A chemical solvent is a substance that dissolves another to form a solution. For example, water is a solvent for sugar. Unfortunately, many chemical solvents are hazardous to the environment. One eco-friendly chemical solvent is chloroform, also known as trichloromethane (

C H {C l}_{3}

). The table above shows the chemical makeup of one mole of chloroform.
If a chemist starts with

1, 000

grams of chloroform and uses

522.5

grams, how many moles of chlorine are left?

Q. This question along with the next two were asked in the (IIT-JEE, 2007) exam. Let us try them out!

Chemical reactions involve interaction of atoms and molecules. A large number of atoms/molecules (approximately

6.023 \times 10^{23}

are present in a few grams of any chemical compound varying with their atomic/molecular masses. To handle such large numbers conveniently, the mole concept was introduced. This concept has implications in diverse areas such as analytical chemistry, biochemistry, electrochemistry, and radiochemistry. The following example illustrates a typical case, involving chemical/electrochemical reaction, which requires a clear under-standing of the mole concept.

A 4.0 M aqueous solution of NaCl is prepared and 500 mL of this solutionn is electrolyzed. This leads to the evolution of chlorine gas at one of the electrodes (atomic mass of Na is 23 and Hg is 200) (1 F = 96500 C).

The total number of moles of chlorine gas evolved is

Q. Give chemical equation for :
(i) The laboratory preparation of methane from sodium acetate.
(ii) The industrial preparation of methanol from water gas.
(iii) The reaction of one mole of ethene with one mole of chlorine gas.
(iv) The preparation of ethyne from 1, 2-dibromoethane.

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