[peterschmidt3943]

But I have a question again here: why do we take 0,2 time 2 and not 0,1 ? I mean, it says that 0,1 mol of NaOH react, or not?

[peterschmidt3943]

Well, I think I got it now: we got 0,2 mole of diprotic acid, so twice the amount of NaOH.

If you do the math: 0,2/0,1=2

2*0,1=0,2

0,2* 2 (since we got two moles of NaOH)= 0,4.


right?

[DrCMS]

Well, I think I got it now: we got 0,2 mole of diprotic acid,
right?

No, you have 30cm³ of a 0.2mol per dm³ solution.  How many moles is that?

[peterschmidt3943]

6 moles?

[DrCMS]

No.  Stop randomly guessing.

What is 30cm³ equal to in dm³?

[peterschmidt3943]

3 dm^3

[peterschmidt3943]

so we got 3*0,2 moles of the acid...

since we got two molecules NaOH, we need 1,2 moles of NaOH.
12/0,1= we need 12 dm^3 (or 120 cm^3) of NaOH right?

[DrCMS]

Yes 30cm = 3dm but 30cm³ ≠3dm³

[peterschmidt3943]

0,03 dm^3 ...

[peterschmidt3943]

But my last post was basically ok, right?

[peterschmidt3943]

by the way: the solutions are also stated in cm^3...

so, I think that one can get to the soultion as follwoing:

30*0,2=6moles are used of the acid.

6/0,1=60*2=120cm^3 are needed... right ?

[sjb]

by the way: the solutions are also stated in cm^3...

so, I think that one can get to the soultion as follwoing:

30*0,2=6moles are used of the acid.

6/0,1=60*2=120cm^3 are needed... right ?

Maybe, but your error cancels. What does mol dm–3 mean? How would you answer if one volume was needed in dm³ and the given was in cm³?

[Enthalpy]

mol×dm^–3 means mol/dm³.
For units as for other exponentials, a negative exponent means "divide".

By the way, the ISO recommends this use, rather than the divide "/" sign which is sometimes meant to apply to several units that follow.
Like J/(kg×K) is sometimes erroneously written J/kg×K while J×kg^-1×K^-1 is unequivocal.

[sjb]

mol×dm^–3 means mol/dm³.
For units as for other exponentials, a negative exponent means "divide".

By the way, the ISO recommends this use, rather than the divide "/" sign which is sometimes meant to apply to several units that follow.
Like J/(kg×K) is sometimes erroneously written J/kg×K while J×kg^-1×K^-1 is unequivocal.

True, but not necessarily appropriate to the question in hand.

[Enthalpy]

Yes. I had misinterpreted this:

how can we translate dm^-3 into other units ? like, for example, in cm^3 or m^3?