Concentation of Citric Acid in Fruit Juice

[Gurvir]

Homework Statement

This is a lab for Chemistry in grade 12.

I'll give some basic info I have.

Juice substance is Tang.
A solution of juice is prepared by dissolving 4.00 grams of crystals in 100.0 mL of solution. The juice solution is then titrated using a given solution of sodium hydroxide. Phenolphthalein is used as an indicator.

Here is my observations,

Trial # NaOH(aq) added (mL)
Trial 1 3.31
Trial 2 3.18
Trial 3 3.27

Homework Equations

a) find mol/L of acid (I can do this but I cannot figure out the balanced equation)
b) how many grams of pure citric acid is in 100 g of tang (as a percent mass)
*Citric Acid is in your databook. Assume it loses 3 hydrogens.
My teacher said you shouldn't need the formula of the Tang

The Attempt at a Solution

This is all I can think of, I do not know what it will turn into.

C₃H₅O(COOH)_3(aq) + NaOH_(aq) ==>

 

[Borek]

You are on the right track.

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

 

[Gurvir]

You are on the right track.

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

I think I understand it more now!

Let me see,

C₃H₅O(COOH)_3(aq) + 3 NaOH_(aq) ==> C₃H₅O(COO)_3(aq) + 3 H₂O_(l) + 3 Na_(s)

But there wasn't any solid from the reaction so I'm not sure where the Na_(s) goes, does it just separate or get added onto one for the formula's?

 

[Borek]

No no, that was completely wrong. Your product will be a sodium salt!

 

[Gurvir]

No no, that was completely wrong. Your product will be a sodium salt!

--
buffer calculator, concentration calculator
pH calculator, stoichiometry calculator

What? Now I'm confused again, how does that work? Please tell me asap, I don't have long until I have to have this lab complete.

Why would it be NaCl? That doesn't make sense with anything. Cl wasn't even part of the experiment. It can't be created through thin air.

C₃H₅O(COOH)_3(aq) + 3 NaOH_(aq) ==> C₃H₅O(COO)_3(aq) + 3 H₂O_(l) + 3 Na_(s)

This makes sense to me, I don't know where NaCl would go.

 

[Bohrok]

A salt in chemistry isn't necessarily table salt (NaCl) but an ionic compound you get, along with water, after the neutralization of an acid and [STRIKE]salt[/STRIKE] base.

You wouldn't actually have C₃H₅O(COO)_3(aq) and Na_(s), but rather C₃H₅O(COO)₃^3-_(aq) and Na⁺_(aq). The first one ionized since it lost H⁺ ions while the Na is still an Na⁺ ion. It could also be written as Na₃C₃H₅O(COO)_3(aq)

 

[Borek]

Bohrok already nicely explained what is going on. Salt name is sodium citrate.