Exercises

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Page ID: 54365

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Q9-1

Draw out the Lewis structure for phosphoric acid and circle the acidic hydrogens. (how many are there?)

Q9-2

There are three different salts (conjugate bases of phosphoric acid) – draw out structures each one. sodium dihydrogen phosphate (NaH₂PO₄,) disodium hydrogen phosphate (Na₂HPO₄), and sodium phosphate (Na₃PO4)

Q9-3

What is the pH of a buffer that is 0.15 M in both sodium dihydrogen phosphate (NaH₂PO₄ pKa 7.2) and disodium hydrogen phosphate (Na₂HPO₄)?

Q9-4

What would be the pH of the buffer if 0.01 mol HCl were added to the buffer? (Write out the equation to show which part of the buffer it would react with.)

Q9-5

What would be the pH if 0.01 mol NaOH were added to the buffer?

Q9-6

Carbon dioxide is involved in a number of reactions (in any aqueous system).

It can dissolve in water to give carbonic acid (pKa 6.4), which can then react with more water to give an acidic solution.

H₂O + CO₂ ⇌ H₂CO₃+ H₂O ⇌ HCO₃^– + H₃O⁺

A) What would happen to the amountof carbon dioxide in solution if you increased the pH of the system by adding base?

Write out the reactions involved.

Q9-7

Draw the unprotonated form of ATP showing how the molecule is stabilized by intracelular fluids (hint you are > 70% water)

Q9-8

If the standard Gibbs energy change for the oxidation of glucose is – 2870 kJ/mol, how many moles of ATP could be produced from ADP + Pi? Under standard condiitons Gibbs energy of hydrolysis of ATP is – 29 kJ/mol