. A lake with a volume of 106 m

3 receives 10 m3
/s of inflow containing 0.1 mol/m3
of
a chemical. The chemical reacts with a first-order rate constant of 0.02 h-1
. The
outflow from the lake is also 10 m3
/s. Assume there was no chemical in the lake at
the beginning. What will be the concentration changing rate of this chemical in this
lake? Assume the concentration of such chemical at certain time is x mol/m3
in the
lake. (10 marks)