A⟶B is a first order reaction. The concentration of A is decreased from x mol L−1 to y‌mol‌L−1 in 100 min . What is the average velocity of the reaction in mol L−1min−1?
We want to find the average velocity (rate) for the reaction as A goes to B when the amount of A drops from x to ymol∕L in 100 minutes. The change in the concentration of A is: ∆[A]=y−xmol∕L This tells us how much A has changed in value. The average velocity means how much A changes per minute. We can find it by dividing the total change in A by the time taken: Average velocity =‌
∆[A]
∆t
where ∆t=100 minutes. So, Average velocity =‌
y−x
100
molL−1min−1 If you need the answer as a positive value (since rates are usually positive), write it as ‌