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Finding chemical equations in a phosphate buffer system

Dear tutor:
I am a better than average Chem student, however, I am stumped on two problems related to 'the phosphate buffer system' and one other concerned with CO2 gas blown through a straw in H2O.

As follows:
1) The phosphate buffer system used in this exercise consists of the phosphate buffer pair known as KH2PO4 & K2HPO. I need to write the chemical equation which occurs when H2SO4 is added to this buffer system.
2) Also, the chemical equation that occurs when NaOH is added to this same 'phosphate buffer system'.
3) If you breathe H2O into a straw the H2O becomes more acidic. How is this represented by an equation? I know it is H2CO3, but does it disassociate into ions in the solution?

Thank you,


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Solution Preview


First of all we have to recognize that buffer solutions can consist of either 1) weak acid and its salt with strong base or 2) weak base and its salt with strong acid. In this case your weak acid is H2PO4- and its salt is K2HPO4 (because we can form K2HPO4 from H2PO4- as a weak acid - H2PO4- = H+ + HPO42- - and strong base KOH). Now, if H2PO4- is a weak acid, HPO42- must be a strong base (by acid-base theory). Hence, in your buffer ...

Solution Summary

This solution provides step-by-step explanations in 330 words for writing chemical equations when there is a reaction in a buffer system between an acid and a base.