Chapter 18 Section 1 ChemicaL Equilibrium p. 589-5971 Chemical Equilibrium Chapter 18 Modern...

Chapter 18 Section 1 ChemicaL Equilibrium p. 589-597

1

ChemicalEquilibriumChapter 18

Modern ChemistrySections 1 & 2

The Nature of Chemical EquilibriumShifting Equilibrium


2

The Nature of Chemical Equilibrium

Section 18.1


3

Reversible Reaction Chemical Equilibrium Equilibrium Expression Equilibrium Constant LeChatelier’s Principle

Vocabulary

Insert Holt Disc 2


4

Reversible Reactions

Insert Holt Disc 2

Insert Glencoe Disc 1


5

Products can react to re-form the reactants.

Must occur in a “closed” system

2HgO(s) 2Hg(l) + O2(g)

2Hg(l) + O2(g) 2HgO(s) Both of these reactions

occur simultaneously 2HgO(s) 2Hg(l) + O2(g)

Reversible Reactions


6

Rate of its forward reaction equals the rate of its reverse reaction ….

and the concentrations of its products and reactants remain unchanged

Eventually all reversible reactions will reach eq. if the system is closed and conditions don’t change.

Eq. is dynamic – always in motion.

Chemical Equilibrium


7p. 591

Reacti

on

Rate

vs t

ime


8

Equilibrium Demonstration


9p. 591

Reaction Rate vs. Time

Rateforward = Ratereverse


10

What is “favored” at Eq? At equilibrium

reactants are favored

neither is favored

products are favored

equal rates!


11

n A + m B x C + y D

Dependant on temperature Independent of initial concentrations

Equilibrium Expression

[C]x [D]y

[A]n [B]mKeq =

[ ] = concentration in

mol/L

x, y, n, m = coefficients

=productsreactants


12

If Keq is large (>1) then products are favored at eq.

If Keq is small (<1) then reactants are favored at eq.

Equilibrium Constant

PRODUCTSREACTANTS

Keq =

PRODUCTS

REACTANTS

Keq =

Pure liquids and solid are omitted.


13

Equilibrium Constants Table


14

An equilibrium mixture of N2, O2 , and NO gases at 1500 K is determined to consist of 6.4x10–3 mol/L of N2, 1.7x10–3 mol/L of O2, and 1.1x10–5 mol/L of NO. What is the equilibrium constant for the system at this temperature?

Keq = 1.1 x 10−5

Sample Problem p. 594


15

At equilibrium a mixture of N2, H2, and NH3 gas at 500°C is determined to consist of 0.602 mol/L of N2, 0.420 mol/L of H2, and 0.113 mol/L of NH3.What is the equilibrium constant for the reaction N2(g) + 3H2(g) 2NH3(g) at this temperature?

0.286

Practice Problems p. 595 #1


16

The reaction AB2C(g) B2(g) + AC(g) reached equilibrium at 900 K in a 5.00 L vessel. At equilibrium 0.084 mol of AB2C, 0.035 mol of B2, and 0.059 mol of AC were detected. What is the equilibrium constant at this temperature for this system? (Don’t forget to convert amounts to concentrations.)

4.9 x 10−3



17

A reaction between gaseous sulfur dioxide and oxygen gas to produce gaseous sulfur trioxide takes place at 600°C.At that temperature, the concentration of SO2 is found to be 1.50 mol/L, the concentration of O2 is 1.25 mol/L, and the concentration of SO3 is 3.50 mol/L. Using the balanced chemical equation, calculate the equilibrium constant for this system.4.36



18p. 593

Equilibrium Concentrationsand Keq values


19

For the decomposition reaction of ammonia, 0.75 M of ammonia are added to an empty 1 L flask. When the reversible reaction has achieved equilibrium the concentration of nitrogen in the flask is 0.15 M. Find the equilibrium concentrations of hydrogen and ammonia. Also find the Keq.

Eq. Concentration Problem


20

N2 (g)+3 H2 (g) 2NH3(g)

Determining Eq. Concentrations

Iinitia

l

Cchang

e

Eequil

.

0 M 0 M 0.75 M

0.15 M

+0.15 M

1/3 = 0.15/x

x = 0.45M+0.45 M

0.45 M


21

N2 (g)+3 H2 (g) 2NH3(g)


Iinitia

l

Cchang

e

Eequil

.

0 M 0 M 0.75 M

0.15 M

+0.15 M

1/2 = 0.15/x

x = 0.30M+0.45 M

0.45 M

-0.30 M

0.45 M

If this side is + then the other side is -.


22

For the synthesis reaction of hydrogen and iodine, 0.20M of hydrogen and 0.30M of iodine are added to an empty 1 L flask. When the reversible reaction has achieved equilibrium the concentration of hydrogen in the flask is 0.10 M. Find the equilibrium concentrations of iodine and hydrogen iodide. Also find the Keq.

Eq. Concentration Problem


23

H2 (g) + I2 (g) 2HI(g)


Iinitia

l

Cchang

e

Eequil

.

0.20 M 0.30 M 0 M

0.10 M

-0.10 M

1/1 = 0.10/x

x = 0.10M-0.10 M

0.20 M


24

H2 (g) + I2 (g) 2HI(g)


Iinitia

l

Cchang

e

Eequil

.

0.20 M 0.30 M 0 M

0.10 M

-0.10 M

1/2 = 0.10/x

x = 0.20M-0.10 M

0.20 M

+0.20 M

0.20 M

If this side is - then the other side is +.


25

A 0.20 M solution of HC2H3O2 is 5.0% ionized. Find the equilibrium concentrations of H+, C2H3O2

1- and HC2H3O2, also find the Keq.

answer

Eq Concentration Problem


26

At a specific temperature and pressure, 1.2 moles of hydrogen, 0.40 moles of nitrogen and 1.3 moles of ammonia are put into a closed one liter flask. When allowed to reach equilibrium the amount of ammonia is 1.6 moles. Find the Keq for this system.

N2 (g) + 3H2 (g) 2NH3 (g)

answer

Eq Conc. & Keq Problems


27

When .56 moles of SO3 is placed in a liter container, some of it decomposes. The equilibrium concentrations of SO2 is 0.42 moles / liter. Calculate the equilibrium concentration of O2 and SO3 and the Keq.

O2 = 0.21 M SO3 = 0.14 M Keq = .53

Eq Conc. & Keq Problems


28

Ch 18 Sec 1 Homework

Page 595 # 1-9


29

Ch 18 Sec 1 Homework

Equilibrium Concentrations and Keq Worksheet

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Chapter 18 Section 1 ChemicaL Equilibrium p. 589-5971 Chemical Equilibrium Chapter 18 Modern...

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