equilibrium constants?

Question

The equilibrium constants for three different reactions are
i) Ke = 1.5 x 10^12
ii) Ke= 0.15
iii) Ke= 4.3 x 10^-15

in which reaction is:
a) the ratio of product to reactant larger?
b) the ratio of product to reactant small?

and...

why is it necessary to specify the temp when giving a value for Ke?

any help would be appreciated!! thanks!

Answer 1

for a simple rxn, say
R---> P
the expression for the eq. const is ,
Keq = [P]/[R].

=> the greater the value of [P], the greater is the value of Keq.

it readily follows that,
a) in rxn (i), the ratio of product to reactant is larger.
b) in rxn (iii), the ratio of product to reactant is small.
===== ===== ====== ======== ========= ===========

the eq. const is highly sensitive to temperature. An increase in temp will shift the eq. to the side where heat is absorbed, & a fall in temp. will shift the eq to the reverse side of the first one(according to Le-Chatelier's principle).
that is why it's necessary to cite the temp. when giving the value of Keq.

Answer 2

Remember that the K value is a ratio of concentrations of PRODUCTS (raised to proper exponents) OVER REACTANTS (likewise raised to appropriate exponents. The larger K is, the more products are favored, as concentrations of products far exceed that of reactants at equilibrium. The smaller the number, the more in favor of reactants equilibrium will be. Puny number means more reactants than products. (You do your own homework and figure out which choice goes with which situation based on my translation of it for you...that's as far as I'll go for you. Do
some thinking now that you have the information you need.)

K depends on Temperature. Kp ESPECIALLY depends on temperature. Reactions that consist mostly of gases (for example) will favor the side of the reaction that has the greatest number of moles of gas. Likewise, higher temperatures will shift equilibrium in that direction - in favor of the larger number of moles of (all) gases. You pick it up from there, sport...

Answer 3

Yup, I agree with Paul on this one. When the value of Keq is greater than 1, products are favored, when less than 1, reactants are favored. This is because not enough reactant is being produced or vice versa. For Temperature, yes, It does affect Keq. Remember what affects equillibrium? It is size of particles, temperature, and concentration of particles. If any of these factors is changed, you can expect an equilibrium shift to occur. You can have more reactant being produced than products when the Keq is less than one. Hope this contributes :)
Particle size because if they are bigger, less surface area is subjected to the elements of the reaction.

Answer 4

Keq is basically the concentration of products divided by reactants. The larger the Keq, the more products you have. Reaction i has the largest ratio of products. Reaction iii has the smallest ratio of products to reactants.

Answer 5

iii)

i)


Kc is dependent upon the temperature.