What is the reason for analyzing a blank in the spectrophotometer before analyzing the standard solution? A. any absorbance of light by the solvent AND the cuvette needs to be accounted for B. any absorbance of light by the cuvetto needs to be accounted for C. so the scattered light is filtered before reaching the photodiode D. to account for any fingerprints on the cuvette E. any absorbance of light by the cuvette and fingerprints needs to be accounted for

A.  any absorbance of light by the solvent AND the cuvette needs to be accounted for

Explanation:

Blank calibrations are usually carried out on the spectrometer to eliminate and account for any readings that would come from absorptions of the curvette, solvents/reagents or anything that is not the main analyte we are testing for.

Hence the blank solution does not contain the analyte itself. Fingerprints should be removed from the curvette as practice. Hence the most suitable answer amongst the options is A.

I hope this was clear ad most of all, helpful.

"you start with 15.67 g mgco3-xh2o, when heated and all the water is removed, you are left with 7.58 g mgco3 only.

therefore, you had 15.67 - 7.58 = 8.09g h2o  

moles of each :

7.58g mgco3 = ? moles = 7.58g / 83.4g/mole = 0.09moles  

8 09g h2o = ? moles = 8.09g / 18g/mole = 0.44moles  

molar ratio between the two by dividing both numbers by the smallest number :

0.09 / 0.09 = 1  

0.44 / 0.09 = 4.8  

mgco3-5h2o"