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#### markosheehan

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- Jun 6, 2016

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- Mar 5, 2012

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The unit of $100\text{ cm}^3$ cancels against the unit of $5.7\text{ cm}^3$.I am confused on a titration question.

I understand most of it but I do not see why they do not multiply their answer by 10 at the end because it says 100 cm^3 of water was analysed but that formula gives answers in moles/L so to make it into a liter they should multiply by 10 but they do not ?

That is, we're left with the ratio between those 2 volumes, which is unit-less.

That leaves the unit of the concentration $M=0.02\text{ g/L}$ (I can't read the subscript), which is already in $\text{g/L}$.

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- Jun 6, 2016

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i am confused on this question though.

here they divide their answer by 4 at the end even though both units are in cm^3

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i also do not understand this question. i understand that they multiply at the end by 5 as there was a dilution factor of 5 but I do not see why they do not divide by 10 as the vinegar was in a 100 cm^3 volumetric flask .

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- Jun 6, 2016

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anyone?

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- Mar 5, 2012

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The given concentration is in $\text{g/L}$.ok. thanks . i think i get it.

i am confused on this question though.

here they divide their answer by 4 at the end even though both units are in cm^3

That is, the number of grams that would be in 1 liter.

Since we're talking about $250\text{ cm}^3$, which is a quarter of a liter, we need to divide by 4.

Again, the concentration is given in $\text{g/L}$, which is the number of grams that 1 liter would have.i also do not understand this question. i understand that they multiply at the end by 5 as there was a dilution factor of 5 but I do not see why they do not divide by 10 as the vinegar was in a 100 cm^3 volumetric flask .

And it's not the number of grams in the original flask - that would be 1/10th.

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- Mar 5, 2012

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Only if they would have asked for the 'grams' (the mass).

But they're asking for the 'concentration'. For concentration the volume is irrelevant - it has been 'divided out'.

So whether we have 1 liter with 60 g/L, or we have 0.1 liter with 60 g/L, they have the same concentration of 60 g/L.

Of course there are 60 grams in that liter, and only 6 grams in the 0.1 liter.

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- Jun 6, 2016

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