[born2dive00]

Ok i have a problem that I need help with.

There is 455mg of 85% phosphoric acid diluted in 1000ml of water, to that is added 176mg of sodium hydroxide.

The question has 3 parts
1. It says calculate how much citric acid needs to be added to decrease the pH to 3.02
2. Which species will be the dominant species the phosphate or the citrate.
3. Calculate how much of each species is present.

I have no clue how to go about doing this and I am not allowed to us a pH meter...
Can someone help me out with this please.

[Babcock_Hall]

You have to show your work or provide your thoughts before we can help.  However, I will give you a small hint.  I would calculate the moles of two of the substances as a starting point.  One also needs to decide upon the meaning of the word "dominant," which I would take to mean in highest concentration.