Equilibrium Constant

What you can expect to learn from this page:

-Able to understand structure of equation.

-To understand it well enough to be able to know diffrences when numbers are changed.

Background Summary:

Reaction: When a substance is changed to a new substance.

Reaction Rate: How fast reaction takes place.

Equilibrium: When both sides of the equal sign are reacting at the same rate, therefore cancelling each other out.

Activation Energy: The energy needed to be obtained for a reaction to occur.

Catalyst: Quickens the reaction process by lowering the activation energy.

Collision Model: Shows reaction rates by colliding molecules which can be effected by temperature, energy, orientation, and quantity. This effects if they are able to react.

 

Lesson:

aA   +   bB    -->  cC   +   dD=
Reactants     -->   Product

The uppercase letter stands for the actual value of the molecule.

The lowercase letter stands for the coefficient.

   K=         [C]^c  [D]^d      -->  Products
[A]^a [B]^b               Reactants

  K=                                     

• Always stays constant
• Never changes the equilibrium constant
• Always must keep same constant even if numbers are changed.

 

Example 1: 

   2NO₂   -->    2NO + O₂

Reactant    -->    Product

Equilibrium Constant:   

K= [NO]²  [O₂]  
[NO₂]²

at Equilibrium:

      [ N O                
[NO]= 1
[O₂]= 2
[NO₂]= 5

K=  (2)
 

(1)² (2) =K
25  

   2    =K
25

K= 0.08

 

1.What is the expression for C₂H₄ + 4O₂ --> 2CO₂ + H₂O?

C₂H₄ + 4O₂ --> 2CO₂ + H₂O

Multiple Choices

A)[2CO₂] [H₂O]
es[C₂H₄] [4O₂ ]

B)[2CO₂]+ [H₂O]
es[C₂H₄] + [4O₂ ]

C)[CO₂]² [H₂O]
se[C₂H₄] [O₂ ]⁴

D)[CO₂]² + [H₂O]
se[C₂H₄] + [O₂ ]⁴

The expression always goes Products over Reactants,

so the expression is going to be.

[CO₂]² + [H₂O]
[C₂H₄] + [O₂ ]⁴

Example 2: Same equation different numbers

[No] = 2               changed to 2       
[O2] = 2               stayed the same                             
[NO2] = ?             is unknown

 

K=  [C]c  [D]d    -->  Products     
[A]a [B]b               Reactants

  .08 =  (2)(2)
X XX

 

.08= (4)(2)
XXX
.08= 8
XX X

 

                     .08X =8        divide .08 from each side

                       X= 100

Quicktips:

• if a element is solid its not included in equilibrium constant equation

2. What is the Equilibrium Constant :

 

• N2(g) + 3Cl2(g) <--> 2NCl3(g)
• when [N2] = 0.25M, [Cl2] = 0.10M and [NCl3] = 2.43 x 10-3
  

A)K=[2.43 * 10 ^-3] o= .00243 =.00243 = .2436075
ellllol 0.25 + (0.10)³ o.25+100 ll100.25

B)K=[2.43 * 10 ^-3] o= .00243 =.00243 = .0000972
ellllol 0.25 * (0.10)³ o.25*100 lloll25

C)K=[2.43 * 10 ³] o= lll2430 o=2430 = 9716.113555
ellllol 0.25 + (0.10)^-3.25+.001 l.25010

D)K=[2.43 * 10 ³] o= lll2430 o=2430 = 97200
ellllol 0.25 * (0.10)^-3.25 *.001 ol.025

K= [NCl3]2 = [2.43 X 10 -3] = .00243 =
[N2] [Cl2]3 0.25 X (0.10)3 . 25 X 100

.00243 = .0000972 Put numbers in correct order which is product over reactant

25

3. Which is the correct way to write this reaction in a equilibrium constant equation:

H₂O(g)+ C(s) -->H₂(g) + CO(g)

A)[H₂O] [CO]
eoos[H₂O]

B)o [H₂O]
es[H₂] [CO]

C)[H₂O] [C]
es[H₂] [CO]

D)[H₂] [CO]
es[H₂O] [C]

 

 

 

 

Homework (if any):