Average [NaOH] from step 1

sarah1004 · Oct 31, 2009, 04:21 PM

standardization of NaOH solution:
a)volume of 6.0M NaOH solution used: 20mL
b)approximate[NaOH] after dilution to 400mL: 0.5M
c)weight of empty flask: 86.525g
d)weight of flask plus KHP: 87.253g
e)weight of KHP: 0.728g
f)moles of KHP: 0.00356mol
g)moles of NaOH: same answer as moles of KHP
h)initial buret reading: 0mL
i)final buret reading: 28.49mL
j)volume of NaOH used up: 28.49mL
k)[NaOH]: 0.12496M
l)Average [NaOH]: 0.11421M (I just didnt write sample2 list on here)

Determination of percent Acetic Acid in an unknown vinegar:
Initial volume of NaOH in the buret: 0
Final volume of NaOH in the buret: 17.5
Volume of NaOH used to reach the end point: 17.5
Average [NaOH] from step 1:________________________
Moles of NaOH used to reach the end point: ______________
Moles of acetic acid present in 10mL sample:_______________

Please help on these three blank space for me and
step 1 is preparation of 0.3M NaOH solution-rinse your graduated cylinder with a few protions of distilled water.
just in case for step 2 is measure about 20mL of 6.0M NaOH solution.

Please help me

Unknown008 · Nov 1, 2009, 10:00 PM

Ok, since the mole ratio is 1:1, you have the same number of moles of acetic acid reacting with the number of moles of NaOH.

The equation, if you want to know is:

$NaOH + CH_3COOH \rightarrow CH_3COONa + H_2O$

So, you have the number of moles of acetic acid in 10 mL

sarah1004 · Nov 1, 2009, 10:13 PM

Ohh so moles of acetic acid present in 10mL sampel is just same answer as moles of NaOH used to reach emd point , correct? two answers are same , corret??

And do you know if only one hydrogen in acetic acid acts as an acid, write a balanced chemical reaction between acetic acid and sodium hydroxide.

CH3COOH+NaOH---->NaOOCCH3+H2O ??

Unknown008 · Nov 1, 2009, 10:30 PM

Yes, exactly!

Yes, only one does. The H in CH bond does not act as an acid, but the H in the COOH does. It's the case for all organic compounds, as far as I know.

The equation is already balanced

sarah1004 · Nov 1, 2009, 10:34 PM

Thanks

I think its gonna be last question

If initial volume of NaOH by mistake 1mL rather than 0mL.
what happens to the moles of NaOH? higher , lower , no effect, why?
I think its lower

what effect does it have on the moles of acetic acid?
lower

Is it correct?

Unknown008 · Nov 1, 2009, 10:39 PM

Less amount of solution means less moles of NaOH used. In turn, you had less moles in 10 mL Since it's less, you have a more diluted acetic acid.

So, yes!

sarah1004 · Nov 1, 2009, 10:41 PM

Thankssss

Thank you so much you are so nice person in the world!

have a great night

Unknown008 · Nov 1, 2009, 10:42 PM

You're welcome! It's 10.45 am here



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