When to use these formulas? (1 Viewer)

[BlueGas]

When do I use CaVa = CbVb
and
n(titrated) = n(initial) - n(reacted) <------ I'm not sure if this is actually the formula, but yeah, I just wanna know when to use these two formulas

 

[Librah]

They're not really formulas, C=n/V is just number of moles per unit volume, what you wrote is just saying that if you don't change the number of moles, n=CV is constant, where C and V are not fixed.

2nd one is just common sense, if you have n moles initially, and m reacted, you have n-m moles remaining. In your case you just used the remaining moles in a titration.

 

[BlueGas]

They're not really formulas, C=n/V is just number of moles per unit volume, what you wrote is just saying that if you don't change the number of moles, n=CV is constant, where C and V are not fixed.

2nd one is just common sense, if you have n moles initially, and m reacted, you have n-m moles remaining. In your case you just used the remaining moles in a titration.

So I won't need the first formula as long as I know C = n/v?

 

[Librah]

So I won't need the first formula as long as I know C = n/v?

CaVa=CbVb is just using n=cv twice when your diluting solutions.

 

[BlueGas]

CaVa=CbVb is just using n=cv twice when your diluting solutions.

And is the second formula I posted the correct one?

 

[MaccaFacta]

When do I use CaVa = CbVb
and
n(titrated) = n(initial) - n(reacted) <------ I'm not sure if this is actually the formula, but yeah, I just wanna know when to use these two formulas

CaVa = CbVb needs to be used carefully. It assumes that a monoprotic acid (e.g. HCl) is reacting with a monoprotic base (e.g. NaOH) - or diprotic with diprotic, or triprotic with triprotic. If you have a diprotic acid, then it takes twice as many moles of a monoprotic base to neutralise it (e.g. H2SO4 with NaOH). I would strongly suggest that you calculate the number of moles as a specific step in solving these kinds of problems, and then refer back to a balanced equation to work out how many moles of the other reactant are needed to neutralise it.