Question

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Answer 1

Answer:

Substance A is mixed with water and it hardens

It is a reversible reaction .

Because later you can dehydrate it and get the substance back. This is the case of Plaster of Paris which is commonly used in fractures.

Substance B is mixed with water and it dissolves to form a solution , it can be a reversible reaction, as salt is dissolved in sea water but it can be retrieved.

Though the above can be an irreversible reaction as when the substance is dissolved in water it may ionize and dissociate.

Some definitions

Reversible reactions

In some chemical reactions, the products of the reaction can react together to produce the original reactants. These reactions are called reversible reactions. They can be represented in the following way:

A + B ⇌ C + D

The symbol ⇌ has two half arrowheads, one pointing in each direction. It is used in equations that show reversible reactions:

the forward reaction is the one that goes to the right

the backward reaction is the one that goes to the left

The reaction mixture may contain reactants and products, and their proportions may be changed by altering the reaction conditions.

Example

Ammonium chloride

Ammonium chloride is a white solid. It breaks down when heated, forming ammonia and hydrogen chloride. When these two gases are cool enough, they react together to form ammonium chloride again.

This reversible reaction can be modelled as:

ammonium chloride ⇌ ammonia + hydrogen chloride

NH4Cl(s) ⇌ NH3(g) + HCl(g)

Answer 2

Answer:

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