CHEM 191 Lecture 12

Question 1

what does a positive change in Gibss energy mean

Answer 1

you have to put energy in to get the reaction to go

Question 2

what does a negative change in Gibbs energy mean

Answer 2

the reaction will give out energy into the surroundings

Question 3

if a process is non-spontaneous what will its reverse be

Answer 3

spontaneous

Question 4

what does the magnitude of ∆G tell us

Answer 4

how far a spontaneous process will proceed towards completion

Question 5

if ∆H is positive and ∆S is negative is the reaction spontaneous (∆rG=∆rH-T∆rS)

Answer 5

the reaction is non-spontaneous at all temperatures

Question 6

if ∆H is negative and ∆S is positive is the reaction spontaneous (∆rG=∆rH-T∆rS)

Answer 6

the reaction is spontaneous at all temperatures

Question 7

if ∆H and ∆S have the same sign is the reaction spontaneous (∆rG=∆rH-T∆rS)

Answer 7

it depends on the temperature of the reaction

Question 8

what is the transition temperature and can we calculate it

Answer 8

the transition temperature is the temperature at which the reaction is not spontaneous but not non-spontaneous - it occurs when the system is at equilibrium and G=0 so we can calculate it

Question 9

what is the Gibbs energy of formation for a pure element

Answer 9

0

Question 10

what are the two ways we can calculate Gibbs energy of formation

Answer 10

using ∆rG=∆rH-T∆rS or
using ∆fG data (similar to hess’s law)

Question 11

what is one way we can drive non-spontaneous reactions

Answer 11

by pairing them with a spontaneous reaction

Question 12

if Q is lesser than K is the ∆rG positive or negative

Answer 12

negative - the reactants are converted to products spontaneously

Question 13

if Q is greater than K is ∆rG positive or negative

Answer 13

positive - the products are converted to reactants spontaneously

Question 14

what is the relationship between Q and ∆G

Answer 14

Q is directly proportional to ∆G