Question

Plotting y= ln [Abs] and x = time to get a straight line means the reaction is first order.

True

False

How are we using the colorimeter probe?

		To measure a change in density.
		To measure a change in absorbance to get concentration.

Answer 1

Plotting y In [Abs] and x- order. time to get a straight line means the reaction is first rue False How are we using the colorimeter probe? To measure a change in density. o measure a change in absorbance to get concentration.

A first order reaction can be represented as $X \rightarrow$ products.

The rate law expression can be expressed as rate $=k[X]$ .

For first order reaction, we plot [X] vs time t to get a straight line with negative slope.

Also absorbance is directly proportional to molar concentration

$A = \epsilon l C$

$A \propto C$

Hence, plotting y= ln [Abs] and x = time to get a straight line means the reaction is first order.

In colorimetery, the absorbance of blank solution, standard solution and unknown solutions are measured. From absorbance of standard solution, the absorbance of blank solution is subtracted to obtain corrected absorbance of standard solution. Similarly corrected absorbance of sample solution is obtained. The corrected absorbance of standard solution is then compared with corrected absorbance of sample solution.