[JayDee]

Please help with the calculations, I am so confused.  I would be so so so greatful!!

Background: Nitrogen is an important nutrient for plant growth, and many nitrogenous fertilisers are currently on the market. These almost invariably contain the required nitrogen as ammonium sulfate. Other nutrients may or may not also be present.
In this experiment, the manufacturer’s claims are checked by adding an excess of sodium hydroxide to a sample of lawn food solution. The excess is then determined by titration against standardised hydrochloric acid.

Place an accurately weighed mass of 1.201 g of the fertiliser into a
250 mL volumetric flask.
Add some distilled water and dissolve as much of the fertiliser as possible. Make up to the mark with more distilled water.
Use a pipette to deliver 20.00 mL of sodium hydroxide (c=0.1000075 mol L-1)
4. Use another pipette to add 20.00 mL of the fertiliser solution to the same conical flask.
5. Add about 50 mL of distilled water to this flask, and then boil the mixture for about 10 minutes. A funnel placed on top of the flask will help prevent the hot mixture from splashing out and will help when adding more water from time to time, so that the volume in the flask stays fairly constant.
6. Repeat steps 1 to 5 with the other two conical flasks. 7. After the flask has cooled, add three drops of phenolphthalein indicator
and titrate using standardised 0.9996 mol L-1 hydrochloric acid. 8. Repeat step 7 with the other two flasks (or more if necessary), until three
concordant titres are obtained. titre obtained = 10.80 ml

Please help with the calculations..
I don't know what to do with the mass and the distilled water at the start... because it is not directly reacting with the NaOH..

[RobertT]

Please show some you're working out so we can actually provide you with the help in the specific areas that you need to. Also it's a requirement in the rules

[Borek]

You will use mass to calculate ammonia percentage in the initial solution. Water is used just to dilute.

This is so called back titration:

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

And calculating titration results in general:

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

[JayDee]

Yeah I know how to do a back titration, i think the wording is just messing me up.
Like I am completely lost about how to start this one

[Borek]

Start with reaction equations, it usually helps.

[JayDee]

(NH4)2 SO4 + 2NaOH → Na2SO4 + 2NH3 + 2H2O

my brain just is not clicking... do i then find out the mol of the hydrochloric acid in order to determine how much NaOH was unreacted?