Answer : The measured absorbance of 0.20 M solution is 0.52
Explanation :
Using the proportionality relationship between concentration and absorbance, we use:

where,
= concentration of solution 1 = 0.10 M
= concentration of solution 2 = 0.20 M
= absorbance of solution 1 = 0.26
= absorbance of solution 2 = ?
Now put all the given values in the above expression, we get:


Therefore, the measured absorbance of 0.20 M solution is 0.52