Answer: The molar mass of the given compound is 
Explanation:
In molecular formula of
there are two chlorine atoms and one calcium atom.
The atomic mass of the calcium = 40.07 g/mol
The atomic mass of chlorine = 35.5 g/mol
Molar mass of the guven compound is :

The molar mass of the given compound is 
Preparing 15 mg/gl working standard solution from a 20 mg/dl stock solution will require the application of the dilution principle.
Recalling the principle:
initial volume x initial molarity = final volume x final molarity
Since we were not given any volume to work with, we can as well just take an arbitrary volume to be prepared. Let's assume that the stock solution is 10 mL and we want to prepare 15 mg/gl from it:
Applying the dilution principle:
10 x 20 = final volume x 15
final volume = 200/15
= 13.33 mL
This means that in order to prepare 13.33 mL, 15 mg/l working standard solution from 10 ml, 20 mg/dl stock solution, 3.33 mL of the diluent must be added to the stock solution.
More on dilution principle can be found here: brainly.com/question/11493179
It contributes by breathing. CO2 is carbon dioxide we breath it out and plants convert it into oxygen.