Negative gradient graphs So basically I have a graph of Absorbance on y-axis against Time on x-axis and it is a negative curve. So this will give me a negative slope gradient. My question is how to reason the negative gradient. Do I write down the rate of concentration as a negative value and just reason it by saying that by being negative it means that the concentration is decreasing?
Yes. Beer's law tells us that the absorption is the product of path length, extinction and concentration. Thus concentration is absorption divided by the product of path and extinction. The rate of change of concentration (first derivative with respect to time of concentration is the rate of change of absorption divided by the product of path and extinction. If the rate of change of absorption is negative the rate of change of concentration is negative. Concentration is decreasing.