The concentrations of reactants and products for a chemical reaction can be calc

Question

The concentrations of reactants and products for a chemical reaction can be calculated if the equilibrium constant for the reaction and the starting concentrations of reactants and/or products are known

. Part A Carbonyl fluoride, COF2, is an important intermediate used in the production of fluorine-containing compounds. For instance, it is used to make the refrigerant carbon tetrafluoride, CF4 via the reaction 2COF2(g)CO2(g)+CF4(g), Kc=8.00 If only COF2 is present initially at a concentration of 2.00 M, what concentration of COF2 remains at equilibrium?

Express the molar concentration numerically

[COF2] =

Part B Consider the reaction CO(g)+NH3(g)HCONH2(g), Kc=0.680 If a reaction vessel initially contains only CO and NH3 at concentrations of 1.00 M and 2.00 M, respectively, what will the concentration of HCONH2 be at equilibrium?

Express the molar concentration numerically to three significant figures.

[HCONH2] =

Explanation / Answer

1)

consider the given reaction

2 COF2 ----> C02 + CF4

using ICE table

initial conc of COF2 , CO2 , CF4 are 2 , 0 , 0

change in conc of COF2 , C02 , CF4 are -2x , +x , +x

equilibrium conc of COF2 , CO2 , CF4 are 2-2x , x , x

now

Kc = [C02] [CF4] / [COF2]^2

now

8 = [x] [x] / [2-2x]^2

8 = [x]^2 / [2-2x]^2

8 = [ x/ (2-2x)]^2

2.82843 = x / ( 2-2x)

x = 2.82843 * 2 ( 1-x)

x = 0.85

so

at equilibrium

[COF2] = 2 - 2x

[COF2] = 2 - (2 * 0.85)

[COF2] = 0.3

so

0.3 M of COF2 will remain at equilibrium

2)

consider the given reaction

CO + NH3 ---> HCONH2

using ICE table

initial conc of CO ,NH3 , HCONH2 are 1 , 2 , 0

change in conc of CO , NH3 , HCONH2 are -x , -x , +x

equilibrium conc of CO , NH3 , HCONH2 are 1-x , 2-x ,x

now

Kc = [HCONH2] / [CO] [NH3]

0.68 = [x] / [1-x] [2-x]

0.68 ( 2 - 3x + x2) = x

1.36 - 2.04x + 0.68x2 = x

0.68x2 -3.04x + 1.36 = 0

x = 0.504

so

at equilibrium

[HCONH2] = x = 0.504 M

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