Question

Imagine that the reaction in model 1 starts with 100 molecules of A and zero molecules of B. explain why the concentration of substance A will never reach zero.

Answer 1

Answer:

Most of the reactions that we have studied this year have been “forward” reactions—once the reactant has

changed into the product it stays that way. We can assume that eventually the reaction will “finish” when

the limiting reactant runs out. However, in a reversible reaction (one that can take place in both directions), once the product is formed it can turn back into the reactant and a continuous cycle occurs. When

do reactions such as these “finish?” Is there ever an end, and can we predict how much reactant or product

will be present when the reaction is “done?”

Explanation:

Answer 2

Reversible Reaction:

• A reaction in which the reactants are converted to products and the products are converted back to reactants, is called a reversible reaction.
• A reversible reaction is a combination of a forward reaction and a backward reaction.
• Both the forward and backward reactions take place simultaneously.
• A reversible reaction is written as A + B ⇄ C + D

Explanation:

• If we start with 100 molecules of the reactant and zero molecules of the product, the concentration of the reactant will never reach zero.
• This is because, in a reversible reaction, reactants are converted into products, and simultaneously products are converted into reactants.
• This process keeps on going until some equilibrium condition is achieved.
• Since at any given time, some amount of the product is always being converted back into the reactant, the concentration of reactant material is never exhausted.

Therefore, the concentration of substance A will never reach zero.

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