Gibbs And Equilibrium Flashcards
What does the equilibrium constant show?
The ratio between products to reactants in a reversible reaction thus what side the position of equilibrium Is at
What is the value of the equilibrium constant if a reversible reaction is feasible?
It must be bigger than 1
The larger the equilibrium constant…
The more products there are to reactants (in terms of concentration)
So position of equilibrium is to the left and if it’s big enough can eventually reach completion
Reversible reactions with a K value larger than 1 will have a __ Gibbs value?
A negative value as this shows the reaction is feasible in the first place
What is the value of an equilibrium constant if the reaction is NOT feasible
It is below 1
The smaller the equilibrium constant…
There is a higher concentration of reactants to products thus the position of equilibrium is to the left
If it’s very small, the reaction does not occur
The value of Gibbs when the equilibrium constant is below 1 must be…
Positive because the reaction is not feasible
What equation links Gibbs to the equilibrium constant?
🔺G = -RT lnK
To work out the equilibrium constant…
lnk = 🔺G/ -RT
Put to power of e to remove the natural log
If the equilibrium constant is exactly 1…
The Gibbs value is 0 so the reaction does occur
But the concentration of reactants = concentration of products
What units must Gibbs be in for the equation?
J mol-1
Relationship between entropy of system and lnK?
They are directly proportional as shown by combining 🔺G = -RTlnK and 🔺G = -T🔺S system
If entropy of system and lnk are directly proportional..l
The more positive the entropy of the system is… the larger the equilibrium constant
Equation for straight line graph combining equations
🔺G = -RTlnk and also 🔺G = 🔺H - T🔺Ssystem. So…
-RTlnk = 🔺H - T🔺Ssystem. Divide by -RT…. CANCELS OUT THE NEGATIVE
lnK =(🔺H/RT) + (🔺Ssystem/R)
Straight line graph: the y axis and x axis
lnK values = y axis
1/Temperate = x axis
How do we draw one of these graphs?
Work out the equilibrium constant at a range of temperatures
Plot the lnK to 1/T
What is the gradient equal to in these graphs?
-🔺H/ R = gradient
What is the y intercept equal to in the graph?
🔺Ssystem/R
