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Chemistry Forums for Students => Undergraduate General Chemistry Forum => Topic started by: FabioAceRod on June 12, 2017, 01:52:31 PM

Title: Vant Hoff
Post by: FabioAceRod on June 12, 2017, 01:52:31 PM

Hello, I'm having a very basic problem . To calculate de i (vant hoff factor) you do so by the number of ions that come from the molecule in question. But how do you know what Ions are coming . For example NaCl I know that it makes Na+ and Cl-  so its 2. But I know that from experience in other excercises with NaCl, but I think theres a very basic highschool level way to determine that right? (I need chemistry 101 in college but never had a lot of basis before sorry for the noob question) 
Another example is CaCl2 >Ca2+(aq)+2Cl- what?! where does that 2+ come from? why is it 2

Title: Re: Vant Hoff
Post by: Borek on June 12, 2017, 02:04:27 PM

I am not sure what your question is - are you asking why calcium chloride is CaCl₂ and not CaCl or CaCl₃? Or are you asking why CaCl₂ dissociates into Ca²⁺ and 2Cl^-?

In a way in both cases the answer is: properties of calcium (and other alkaline earth metals) are such that calcium is always bivalent. This is the effect of its electronic configuration and position on the periodic table.