Given the equilibrium reaction N2(g) + 3 H2(g) <---> 2NH3(g) + heat, an increase in temperature will:

a) Increase the value of K
b) Decrease the value of K
c) Increase or decrease the value of K depending upon the concentration of reactants
d) Will have no effect on the value of K
e) Will increase or decrease the value of K depending on the concentration of ammonia

To change the value of K in the reaction H2(g) + I2(g) <---> 2HI(g), one would:
a) Increase pressure
b) Decrease the volume of the system
c) Decrease pressure
d) Increase volume
e) Change the temperature

Please help me understand how to figure out these types of problems!

Le Chatelier's Principle is all about which way the reaction will shift when we mess around with a system in equilibrium. In plain English it states that a system in equilibrium will try to undo what we do to it. For a system such as A + B ==> C + D + heat.

If we add A it will shift to the right because that we the system uses up what we added. If we add B the same thing. If we add C it shifts to the left to use up what we added. Same with D. If we add heat, it MUST shift to the left so as to use up the heat we added. For gaseous reactions just remember that increased causes a shift to the side with fewer moles (so as to occupy the smaller volume).

So for #1, write the K expression.
K = (NH3)^2/(N2)(H2)^3
For increase T it must shift to the left (see my discussion above). If it goes to the left then what happens to the substances? NH3 gets smaller while H2 and N2 get larger. If you substitute into K a smaller number for NH3 and larger numbers for N2 and H2, K must get smaller.
For #2 you are asked to change K. There is no reasoning involved here. Pressure, concentration, volume, all of those things SHIFT the equilibrium BUT they do NOT change the value of K. The only thing that can change K is T.

I understand now, thanks a lot!

I omitted a very important word in one of the last sentences. What I wrote was, "For gaseous reactions just remember that increased causes a shift to the side with fewer moles (so as to occupy the smaller volume)."

I should have written, "For gaseous reactions just remember that increased PRESSURE causes a shift to the side with fewer moles (so as to occupy the smaller volume)."

Well, let's see if I can "chemistry" my way through this one!

For the first question, an increase in temperature will affect the equilibrium position of the reaction. According to Le Chatelier's principle, an increase in temperature will favor the endothermic direction of the reaction to absorb the excess heat. So, we can say that the equilibrium will shift towards the side of the reaction that absorbs heat. In this case, it means more reactants will be consumed to produce more products, namely ammonia (NH3). Therefore, an increase in temperature will decrease the concentration of reactants and increase the concentration of products. As a result, it will decrease the value of K (equilibrium constant). So, my answer is b) Decrease the value of K.

Now let's tackle the second question!

To change the value of K in the reaction H2(g) + I2(g) <---> 2HI(g), we need to alter the equilibrium position. Changing the concentration or pressure won't help much because K is only affected by temperature and not concentration or pressure. However, temperature is the one we need to change here. By manipulating the temperature, we can disrupt or establish a new equilibrium position. So, e) Change the temperature is the correct answer.

Hope that helps! Just remember, chemistry can be as tricky as a clown riding a unicycle while juggling bananas! But with some practice, you'll become the chemistry expert in no time!

To determine the effect of temperature changes on the equilibrium constant (K), we need to consider Le Chatelier's principle.

1. For the first question:
Given the equilibrium reaction N2(g) + 3 H2(g) ⇌ 2NH3(g) + heat,
An increase in temperature will shift the equilibrium in the direction that absorbs heat.
Since this reaction is exothermic (heat is on the product side), the equilibrium will shift to the left to counteract the increase in temperature. As a result, the concentration of N2 and H2 will increase, while the concentration of NH3 will decrease.
Therefore, the value of K will decrease because the ratio of products (NH3) to reactants (N2 and H2) will be smaller.
The answer is (b) Decrease the value of K.

2. For the second question:
Given the equilibrium reaction H2(g) + I2(g) ⇌ 2HI(g),
To change the value of K, we need to change the conditions that affect the equilibrium position. In this case, we can change the volume or temperature.
Changing the volume or pressure of a system will not affect the equilibrium constant (K) for a homogeneous reaction. So, options (a) Increase pressure and (c) Decrease pressure can be eliminated.
Changing the volume (decreasing it) will cause the system to shift towards the side with fewer moles of gas to minimize the change. Since there are fewer moles of gas on the reactant side, the equilibrium will shift to the right, resulting in more HI being formed. Thus, the ratio of products (HI) to reactants (H2 and I2) will increase, and the value of K will increase as well.
Therefore, the answer is (d) Increase volume.

Understanding these types of problems involves studying the principles of chemical equilibrium and Le Chatelier's principle. It's essential to know how different factors, such as temperature, pressure, and volume, can influence the equilibrium position and therefore affect the value of K.