CHEM 1032 Lecture Notes - Lecture 14: Reaction Quotient, Equilibrium Constant, Rice Chart

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scarletmoose272

24 Feb 2017

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K tells me how the reaction process is before i reach equilibrium. K > > 1: lots of product will form before equilibrium is reached, equilibrium lies to the right. K < < 1: few products have formed, equilibrium lies to the left. K = 1: reaction proceeds about halfway. Co(g) + h2 ch3oh(g: kc = [ch3oh]/[co][h2] H2(g) + i2(g) 2hi(g: kc = [hi]2/[h2][i2] I can calculate kc from the equilibrium concentrations of the products and reactants. Equilibrium concentrations are dependent on initial concentrations, but the equilibrium constant is independent of the initial concentrations. If you don"t know all of the equilibrium concentrations: you need to know the initial concentration, you need to know at least one equilibrium concentration. Ice table: i = initial, c = change. Multiply by the coefficient: e = equilibrium. How do i know i"m at equilibrium: use the reaction quotient (q): Ratio of products to reactants at any point in the reaction.

Related Questions

Hydrogen is used as a rocket fuel because it is very light and reacts explosively and completely with oxygen. For the combustion reaction 2H2(g)+O2(g)â2H2O(g) what is the likely magnitude of the equilibrium constant K?

1.K<10â3

2.10â3<K<103

3.K=0

4.K>103

PART B

The industrial production of lime (CaO) from calcium carbonate is accomplished via the following reaction:

CaCO3(s)âCaO(s)+CO2(g)

Given the following data:

Temperature (K)	K
298	1.93Ã10â23
1200	1.01

what can be said about this reaction?

1.Lower temperatures result in more lime formation.

2.The reaction makes more lime at higher temperatures.

3.The reaction goes to completion at 1200 K.

4.The equilibrium lies far to the right at room temperature.

PART C

For the reaction

2H2S(g)â2H2(g)+S2(g), K= 1.00Ã10â6 at 1000 K

what can be said about this reaction at this temperature?

1.The equilibrium lies far to the right.

2.The reaction will proceed very slowly.

3.The reaction contains significant amounts of products and reactants at equilibrium.

4.The equilibrium lies far to the left.

PART D

For the reaction

HCONH2(g)âNH3(g)+CO(g), K= 4.84 at 400 K

what can be said about this reaction at this temperature?

1.The equilibrium lies far to the right.

2.The reaction will proceed very slowly.

3.The reaction contains significant amounts of products and reactants at equilibrium.

4. The equilibrium lies far to the left.

Â± Calculating Equilibrium Constants
The equilibrium constant, K, of a reaction at a particular temperature is determined by the concentrations or pressures of the reactants and products at equilibrium.

For a gaseous reaction with the general form

aA+bBâcC+dD

the Kc and Kp expressions are given by

Kc=[C]c[D]d[A]a[B]b

Kp=(PC)c(PD)d(PA)a(PB)b

The subscript c or p indicates whether K is expressed in terms of concentrations or pressures. Equilibrium-constant expressions do not include a term for any pure solids or liquids that may be involved since their composition does not change throughout the reaction. The standard state of a pure substance is the pure substance itself, and although the quantity may change the sample remain pure. The concentration is effectively equal to 1, and will not impact the magnitude of K.
Part A
Phosgene (carbonyl chloride), COCl2, is an extremely toxic gas that is used in manufacturing certain dyes and plastics. Phosgene can be produced by reacting carbon monoxide and chlorine gas at high temperatures:

CO(g)+Cl2(g)âCOCl2(g)

Carbon monoxide and chlorine gas are allowed to react in a sealed vessel at 456 âC . At equilibrium, the concentrations were measured and the following results obtained:

Gas Partial Pressure
(atm)
CO 0.900
Cl2 1.18
COCl2 0.250

What is the equilibrium constant, Kp, of this reaction?
Express your answer numerically.

Kp =
0.235

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Correct
Deriving concentrations from data
In Part A, you were given the equilibrium pressures, which could be plugged directly into the formula for K. In Part B however, you will be given initial concentrations and only one equilibrium concentration. You must use this data to find all three equilibrium concentrations before you can apply the formula for K.
Part B
The following reaction was performed in a sealed vessel at 774 âC :

H2(g)+I2(g)â2HI(g)

Initially, only H2 and I2 were present at concentrations of [H2]=3.10M and[I2]=2.10M. The equilibrium concentration of I2 is 0.0600 M . What is the equilibrium constant, Kc, for the reaction at this temperature?
Express your answer numerically.

Kc =

CHEM 1032 Lecture Notes - Lecture 14: Reaction Quotient, Equilibrium Constant, Rice Chart

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