[jordansnfootball]

Hello guys, I was having a problem on two questions involving titrations and I was wondering if I could get any help with these:


1. Consider the titration of H3C6H5O7 with NaOH. Let’s say that you need to add 0.0363 moles of NaOH in order for the indicator dye to change color. How many moles of H3C6H5O7 must you have had to start? Report answer to the correct sig figs. Do not provide units.


2. Consider the titration of H3C6H5O7 with NaOH. If it requires 0.00364 mol of NaOH to reach the endpoint, and if we had originally placed 16.80 mL of H3C6H5O7 in the Erlenmeyer flask to be analyzed, what is the molarity of the original H3C6H5O7 solution? Include proper units & sig figs.

Help would be much appreciated. Thanks

[Dan]

Please attempt the question

You need to know what H₃C₆H₅O₇ is, have you been given any other information besides that formula?

[Honclbrif]

One mole of NaOH reacts with how many moles of acid?

[jordansnfootball]

H3C6H5O7 is Citric acid...is that what you mean?

[Dan]

Yeah, thanks. Now answer Honclbrif's question.

[jordansnfootball]

@Honclbrif: It reacts with one mole of citric acid

[Borek]

@Honclbrif: It reacts with one mole of citric acid

No. It is not a monoprotic acid.

[jordansnfootball]

For question 1 it asks how many moles of citric acid are needed, so that's what I am trying to figure out

[Dan]

Look up the structure of citric acid. How do you think it will react with NaOH?

[jordansnfootball]

Citric acid has 3 acidic "H's" so it would have a charge of 3-/ NaOH has an basic "OH" so it would have a charge of +1...That means that 3 moles of NaOH will react with 1 mole of citric acid to create water and salt.. is that correct?

[Borek]

1:3 it is. Now please read this page:

http://www.titrations.info/titration-calculation

[jordansnfootball]

I just did #1... is the answer: .0121 moles of H3C6H5O7 are needed?

[jordansnfootball]

For question #2  I'm not sure if its right

0.00364 mol NaOH x 1 mol H3C6H5O7 = 0.001213333 mol H3C6H5O7
                               3 mol NaOH      

16.80 mL x L = .0168L H3C6H5O7
             1000mL


0.001213333 mol =.0722 M H3C6H5O7
    .0168L

[Dan]

For question #2  I'm not sure if its right

0.00364 mol NaOH x 1 mol H3C6H5O7 = 0.00364 mol H3C6H5O7
                               1 mol NaOH      

I thought you told us the ratio was 1:3... You have calculated on a 1:1 basis.

[jordansnfootball]

oh sorry that was a mistake