[cinnamonstar]

 The experiment is to create a calibration curve of urea solutions. You are provided with 10% urea solution, and need to dilute it to several more diluted solutions.
When urea reacts with urease, alkaline ammonium carbonate is produced. Then you titrate with HCl and record how much is needed.

1) What indicator is the best to use for the titration?

2) When making the dilutions, do you need to take the volume of urease into account, or is this correct?:
9cm of 10% urea solution + 2cm water = 9% urea solution

3) Which reaction would complete first, 10% urea solution + urease, or 5% urea solution +urease?
I am having trouble deciding how long to leave the urea and urease to fully react with eachother...

Please help, pleeeeeeeeeeeeeeease 

[Kuahji]

1) You'd need know the equivalence point of the reaction, from there you can choose an indicator that will colorize your mixture after you just exceed the equivalence point. 

2)  I'm unfamiliar with the units being used as volume.  But yes, the volume would need to be taken into account. 

3)  I don't know .  I think the best thing to do first though, is write out an equation for the reaction, then work from there.