No "ion" is electrically neutral. If it's an ion, then it's charged.
First convert grams to moles:
90.0g *(mole/39.997) = 2.250mole
Remember that molarity is moles per liters:
2.250mol/3L = .750 M
There is a shortcut to this Chem question. simply look at this problem as if it were a cooking recipe. you have 7 parts Carbon and 18 Parts Hydrogen for a total of 25 parts. Simply divide 5.2 by 25 then multiply by 7 to get your answer.
(5.2/ 25) 7 = 1.456 moles