# A particular chemical reaction carried out at 40oC takes 2 hours. How long will it take to carry out the...?

reaction at 20 degrees C

0.5 hour
1 hour
4 hours
8 hours

The Arrhenius equation states that for each 10 degree change in temperature, the rate of a reaction will increase / decrease by ca. 2x. Since your temperature dropped 20C, expect the reaction to take 4 times longer, or about 8 hours.

Note that this is a somewhat crude approximation, and will depend on other factors, but 8 hours is a reasonable estimate.
A correct answer cannot be given because it depends upon the type of chemical reaction
It depends on the activation energy for the reaction which you have not given. The reaction will definitely be slower so it cannot be 0.5 hours or 1 hours but it could be either of the other two.
If this is an endotermic reaction, the answer is four hours.
Because to less temperature, less velocity of reaction.

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