PART A: Calculate K for the reaction between bicarbonate and ammonia. (The stand

Question

PART A: Calculate K for the reaction between bicarbonate and ammonia. (The standard free energy change for the reaction is +3.30 kJ/mol. Assume a temperature of 298 K.)

PART B: The bicarbonate and ammonia reaction can couple with the hydrolysis of ATP (such as shown above). What is ?G?rxn for this coupled reaction?

PART C: What is K for this coupled reaction?

Review the subsection in this chapter entitled Making a Nonspontaneous Process Spontaneous in Section 18.8. The hydrolysis of ATP, ATP(ag)H20(ADP(a) P(a) AG -30.5 kJ is often used to drive nonspontaneous processes-such as muscle contraction and protein synthesis-in living organisms. The nonspontaneous process to be driven must be coupled to the ATP hydrolysis reaction. For example, suppose the nonspontaneous process is A + B ? AB (AG" positive). The coupling of a nonspontaneous reaction such as this one to the hydrolysis of ATP is often accomplished by the following mechanism. A + ATP + H2O ? A-Pi + ADP A+ B + ATP + H2O ? AB+ ADP + Pi As long as ? n for the nonspontaneous reaction is less than 30.5 kJ, the reaction can be made spontaneous by coupling in this way to the hydrolysis of ATP Suppose that ATP is to drive the reaction between bicarbonate and ammonia to form carbamate. +H2O OH NH2

Explanation / Answer

A)

?G = - RT ln (K)

3.30 x 1000 = - 8.314 x 298 x ln (K)

ln (K) = -1.332

K = 0.264

B)

For coupled reaction,

?Gocoup = ?GoATP x ?Gorxn

?Gocoup = -30.5 x 3.3

?Gocoup = -100.65 kJ/mol

C)

?GoCoup = - RT ln (K')

- 100.65 x 1000 = - 8.314 x 298 x ln (K')

ln (K) = 40.6244

K = 4.39 x 1017

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