[faizan]

Why the rate of rection continuously decreases with time?

[fledarmus]

What is the equation for the rate of a reaction?

[faizan]

rate of reaction= change in conc. of reactants or products
                       ----------------------------------------   
                                     Time

[fledarmus]

Good - and how does that depend on the concentration of reactants or products?

[faizan]

i dn't undrestand wht r u trying to ask?
Are u talking about rate law?

[fledarmus]

Exactly - rate law.

[faizan]

rate law:rate of reaction z directly proportional to conc. of reactants. With the passage of time the reactants are converted into products so their conc decreases. And as conc. of reactants decreases, the rate of reaction decreases with time. Am i thnking right???

[fledarmus]

Bingo! 

[faizan]

thank you so much for explaining me this. And wht's your style of explanation....me impressed

[juanrga]

rate law:rate of reaction z directly proportional to conc. of reactants. With the passage of time the reactants are converted into products so their conc decreases. And as conc. of reactants decreases, the rate of reaction decreases with time. Am i thnking right???

Think also that otherwise (the rate does not decreasing with time) would imply that the reaction continues forever, which is impossible.