Mathematics

Problem

The acidity (pH) of a fermenting solution is related to the hydrogen ion concentration

H

(in mol L

^{-1}

) by

\text{pH} = -\log_{10} H

. If

H = 10^{-3} e^{-0.02t}

where

t

is the time in hours, the rate of change of pH at

t = 5

h is closest to a)

-0.0087\text{ units per hour}

0.02\text{ units per hour}

0.0087\text{ units per hour}

0.043\text{ units per hour}