A student made measu rements on some electrochemical cells and calculated three

Question

A student made measu rements on some electrochemical cells and calculated three quantities: . The standard reaction free energy AG . The equilibrium constant K at 25.0°C. . The cell potential under standard conditions E His results are listed below. Unfortunately, the student may have made some mistakes. Examine his results carefully and tick the box next to the incorrect quantity in each row, if any. Note: If there is a mistake in a row, only one of the three quantities listed is wrong. Also, you may assume the number of significant digits in each quantity is correct Also note: for each cell, the number n of electrons transferred per redox reaction is 2. calculated quantities cell n (Check the box next to any that are wrong) AG 205. kJ/mol 108. kJ/mol8.33 77. kI/mol 1.06 V O 0.56 V O 0.40 V 1.22 10o 833 x 10 10 In

Explanation / Answer

G° = -nFE°

1. Option = -2*96487*1.06 = 204552 joules or -204.55 kj

2. Option = -2*96487*0.56 = 108064 joules or -108.064 kj

3. Option = -2*96497*0.40 = 77189 joules or -77.189 kj

Now another formula = G = -RTlnk

1. Option = - 8.314*298*ln(1.22*10^-36)

= 204880 joules = 205 kj

2. Option = - 8.314*298*ln(8.33*10^18)

= -107938 joules = -108 kj

3. Option = -8.314*298*ln(3.09*10^13)

= -76957.987 = -78 kj

Here the appropriate values I calculated you can see that all the three values of each part is not same there is difference of negative sign .

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