Mole is equal to mass of the element divided by molar mass of the element. that is
mole=mass/molar mass
From periodic table calcium has a molar mass of 40 g/mol
moles is therefore =800g/40g/mol=20moles
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Explanation:
As the total concentration is given as 1.2 mM. And, it is also given that salt present in the solution is NaCl.
As sodium chloride is an ionic compound so, when it is added to water then it will dissociate into sodium and chlorine ions as follows.

So, it means in total there will be formation of 2 ions when one molecules of NaCl dissociates.
Therefore, concentration of chlorine ions will be calculated as follows.
Concentration of
ions =
= 0.6 mM
Thus, we can conclude that the concentration of chloride ions is 0.6 mM.
Answer: C
Explanation:
Don’t trust the other person it’s not A