[MklStar]

Hi, I'm doing a school assignment and its very irritating  
it involves titration of orange juice and mixing it with other juices
I'm mixing the orange with lemons and pineapples juices
I found that lemons have a high citrus level, that's obvious but pineapples is what's annoying me
Pineapples belong to the Bromeliaceae family right?
and from what I've searched up, it says there are no citrus acid in them
but when i search up pineapple juice, i find that there is citrus acid
Which is it? and if there is citric acid in the juice then i need to know how much because I'm seeing how does mixing it change the citric content within the diluted mixture.

and quick question,
when comparing the orange+pineapple and the orange+lemon mixtures
do i need to have the same dilution rate because for the orange/pineapple, the ratio is 2 orange 2 pineapple 1 water
and the orange/lemon is at 1 orange 1 lemon 8water
does the amount of water affect the results or anything?

[Hunter2]

Did you get the juice from fresh fruits? If not and  you use commercial juices, then you will find citric acid in all of them.

Of course your mixtures and the amount of water have influence of the results.

By the way how do you detect  citric acid. Acidity is not a measure, because other fruit acids in the frutis.

[MklStar]

Yea I bought the juices with no pulp or preservatives
and for testing the citric acid... I'm not sure exactly how to do it cause of the other acids
but the schools saying just to ignore the other acids and yea...
but we titrate it using NaOH with phenolphthalein indicator

and looks like I'm going to have a hard time looking for the citric contents 

[Arkcon]

Citrate is an important molecule for all living things, and is a common way for plants to be acid, although there are other acids available -- look up citric acid cycle to see more.  I get what you're saying -- you recognize that lemons and their relatives are called "citrus fruits" because historically, they are rich industrial sources of citric acid, and that pineapples are more closely related to orchids.  But these are old names, if your research source says pineapple juice has citric acid, it is probably correct -- historical names be dammed.

[MklStar]

hahaha yea i guess
Now i just have to find how water affects the concentration
like errmmm...
there's the c1v1=c2v2 formula but how to i include the water calculations if anyone gets me...
errr...
like i got a lot of different results and each used a different ratio of juice:water
like for orange:pineapple:water
the ratio is 2:2:1 and i get the molarity of 0.0236M
and orange:lemon:water
is 1:1:8, molarity is 0.0246M
orange:lemon:pineapple:water
1:1:1:7, molarity is around 0.0291M
is there any type of calculations i could use so that the water is ignored or soemthing... I'm not sure

[Borek]

It is all about moles and dilution. Number of moles doesn't change just because you add water. However, if you split the solution, and transfer only part of it - you transfer only part of the substance.

[MklStar]

Umm... I don't get what you mean by split the solution...
but err..

heres my method,
i get 20ml of orange juice, 20ml of pineapple and 10ml of water, mix that and only get 20ml from that mixture and titrate it
and for lemon,
i get 10ml orange 10ml lemon  80ml water and mix it and get 20ml of that as well for titrating it
when you say split the solution, do you mean that?

[Borek]

i get 20ml of orange juice, 20ml of pineapple and 10ml of water, mix that and only get 20ml from that mixture and titrate it

So you had 50mL of the mix and took 20mL of it - effectively splitting the solution into 20mL and 30mL. 20mL contains 20/50 of the total citric acid.

[MklStar]

i get 20ml of orange juice, 20ml of pineapple and 10ml of water, mix that and only get 20ml from that mixture and titrate it

So you had 50mL of the mix and took 20mL of it - effectively splitting the solution into 20mL and 30mL. 20mL contains 20/50 of the total citric acid.

Umm... what about the water that was added? and not all of the juice is citric acid.. there are other acids in there as well but I'm not sure how to calculate those, do i just put it into percentages or something?

[Borek]

So you had 50mL of the mix and took 20mL of it - effectively splitting the solution into 20mL and 30mL. 20mL contains 20/50 of the total citric acid.

Umm... what about the water that was added?

That was included in the 50mL - 20+20+10=50.  No matter how much water you add, amount of acids present in the sample doesn't change, what changes is the volume and the concentration. This is mass conservation at work.

and not all of the juice is citric acid.. there are other acids in there as well but I'm not sure how to calculate those, do i just put it into percentages or something?

You can't do anything about it - all you can do is to report sum of all acids together. You don't have enough data to list them separately.

[MklStar]

Oh.. smart.  haha
thank you very much mate
the rest of my assignment should be fine.

[darincasey]

If the juice had been taken out directly from the fresh fruits it wil definately be pure that is free of acids.But if one is prefering readymade or commercial juices den it is containig some proportion of acid.

[Borek]

If the juice had been taken out directly from the fresh fruits it wil definately be pure that is free of acids.But if one is prefering readymade or commercial juices den it is containig some proportion of acid.

Apart from the fact that it was posted by a spammer, it is completely off. Fresh fruits contain acids, period.