This is even more of a theoretical question. Let"s say that we are given various aqueous solutions and also we are asked to pick the one with the greatest freezing suggest depression, which carry out we choose? Is tright here a pattern? carry out we choose the one with salts inside of it?

Example question

Which aqueous solution exhibits the biggest freezing point depression? $$eginalign(mathrmA)& 1.0 mathrmM ceKBr & (mathrmC)& 0.5 mathrmM ceMgCl2 \(mathrmB)& 0.75 mathrmM ceC6H12O6& (mathrmD) & 0.25 mathrmM ceGa2(SO4)3endalign$$

currently this question is a little bit different because it has actually concentrations, so execute we choose the one via the highest concentrations or the one with salts?


The answer is A)

But my hypothesis is that we only look at the ones that has salts/ions inside of them and also then the one with the highest concentration. Please let me recognize if this is correct or not

homework-related aqueous-solution options
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edited Dec 23 "16 at 1:17

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asked Dec 23 "16 at 1:03

John RawlsJohn Rawls
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Freezing point depression is a role of the amount of liquified substance — but substance need to be treated as distinct particles rather than compound.

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This is an important distinction bereason ionic compounds, once they disresolve in water, commonly sepaprice into hydrated anions and also hydrated cations — two distinct species as much as freezing suggest depression is involved.

Therefore, for ionic compounds you first must recognize just how many type of individual ions are produced and also then multiply that by the in its entirety concentration. In your examples:

$1~mathrmM ceKCl$. One cation, one anion. Thus, tbelow are two moles of dissolved pwrite-ups per mole of compound; offering $2~mathrmM$ reliable particle concentration.

$0.75~mathrmM ceC6H21O6$. This compound is not ionic. Hence, it does not dissociate and one mole dissolved provides one mole of particles. $0.75~mathrmM$ efficient pwrite-up concentration.

$0.5~mathrmM ceMgCl2$. This again is ionic yet we acquire two moles of anions per mol of compound in addition to one mole of cations. Thus three moles of ions per mole of compound. Effective pwrite-up concentration $1.5~mathrmM$.

$0.25~mathrmM ceGa2(SO4)3$. Here, we have actually a complete of 2 moles of cations and also three of anions per mole of compound. Therefore, the effective pshort article concentration is five times the original or $1.25~mathrmM$.

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The actual formula for freezing allude depression is based on a constant factor of levels per liquified mole; and also this evaluation was provided to confirm that ionic compounds separate into ions and also to determine molecular weight in the past.