CHAPTER 13

An Easy Chap- Just Read!

A basic goal of Chemistry is to predict the extent to which a reaction can be expected to occur.

K’s allow us to make such predictions…

See OH #2 "The Classic"

See Fig 13.2- How do we know when we have reaction equilibrium?

K_c =        [NO₂]²

This is a constant provided what is true?

*Know Equ 13.2 by heart on p.434

Another classic esp. #13.1

(How would you know you reached equilibrium here?)

Know Coefficient Rule

Reciprocal Rule

Multiple Equilibrium Rule

When you combine (i.e. add) individual equations you Multiply their K’s to obtain an Equ. Constant for the Net Reaction.

K_(net) = K₁ x K₂

Gaseous Phosphorus PentaChloride* Decomposes to Gaseous Phosphorus Trichloride and Chlorine. Suppose

2.00 mole of Phosphorus Pentachloride in a 2.00 L Vessel comes to Equilibrium. What are the Equilibrium Concentrations?

K_c= 1.0 x 10^-3

See p. 447

N₂ + 3H_2« 2NH₃ + 92.2kJ

1. Add H₂ to System
2. Remove NH₃ [See p. 449] mistake also
3. Decrease the Volume (p.450)

Read Well p.451

4. Temp. Goes Up (p.452)
5. You Add a Catalyst
6. You Raise the Press by Adding Ar. Gas.

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K_p = K_c x (RT) ^{D n(g)}

^{T is the absolute temp}

^{D n(g)} ® change in moles of gas

For the above K_c = 9.5

    R = 0.0821 at 300° C, What is K_p =?.

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Fritz Haber invented synthesis of ammonia from it’s elements.

1. Write the Equation.
2. The Expression for the Equ. Constant.
3. Given K_c = 650 @ 200° C

K_c = .50 @ 400° C

Find D H in kJ

4. Given Above and Your Solution to #3, Find K_c at 600° C.

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Name Period________

You have the Following World Famous A and B. They React as Follows:

A_(g) + 2B_(g)« AB_2(g)

If the Initial Concentrations are

[A]_o= 0.100M; [B]_o= 0.200M; [AB₂]_o = 0.050M,

At Equilibrium Little Becky Chemist Finds [AB₂] to be 0.025M.

What is [A]; [B] Equilibrium Concentrations?

What is K_c?