Calculating+for+Equilibrium+C(K)onstant

In order to find rate, the equation was: rate=k[A]^m[B]^n ;

In order to find the equilibrium, we must calculate the constant (//for a given temperature and pressure//), using the formula:

Keq=[products]^coefficient/ [reactants]^ coefficient

However, there are a few problems with the equation: 1. It cannot include solids (because they do not change in concentration) 2. Solvents are not included

Ex. BaCl2(aq) + Na2SO (aq) <====> 2NaCl(aq) + BaSO4(s)

Keq= [NaCl] ^2/[BaCl2] [NaSO4]

Therefore, if more BaCl2 is added,

[BaCl2] = increases [NaSO4] =decreases [NaCl] = increases [BaSO4] = no change (because it is a solid, there is a change in density, but no change in concentration)


 * BUT**, the constant does not change because //IT IS A CONSTANT// //VALUE// =]

Homework Questions:

1(a) List three environmental factors that may affect the position of a chemical equilibrium. Briefly explain how rate theory explains the effect in each case. (b) List two factors that do not affectthe position of equilibrium.

2. For each of the following chemical systems at equilibrium, use Le Chatelier's principle to predict the effect of the change imposed on the chemical system. Indicate the direction in which the equilibrium is expected to shift, if at versus time, plotted from just before the possible change to the established equilibrium. (a) (b) (c)

(d)

3. The following equation is important in the industrial production of nitric acid. Predict the direction of the equilibrium shift for each of the following changes in a closed vessel. Explain any shiftin terms of changes in rates of the forward and reverse reactions. NH3(g) + 5O2(g) ↔ 4NO(g) + 6H2O(g) + energy (a) 02(g) is added to the system (b)The temperature of the system is increased (c) NO(g) is removed from the system (d)The pressure of the system is increased by the decreasing the volume of the reaction vessel (e) Argon gas is added to the system without changing the volume

4. In a solution of copper (II) chloride, the following equilibrium exists: CuCl42-(aq) + 4H2O(l) ↔ Cu(H2O)42+(aq) + 4Cl-(aq) dark green blue Predict the shift in the equilibrium and draw a graph of concentration versus time for relevant reactants to communicate the shift after the following stresses are applied to system: (a) Hydrochloric acid is added (b)SIlver Nitrate is added

5. The two oxyanions of chromium(IV) are the orange dichlormate ion, and the yellow chromate ion. Explain why a solution containing the following equilibrium system turns yellow when sodium hydroxide is added. Cr2O72-(aq) + H2O(l) ↔ 2CrO42-(aq) + 2H+(aq) orange yellow

6. Identify the nature of the change imposed on the equilibrium system at each of the times indicated A, B, C, D, E. C2H4(g) + H2(g) C2H6(g) + energy

Answers: //1.// (a) //__Concentration Changes__ __Action Increasing rate of: At the new Equilibrium State:__ Increase of reactants Forward reaction Less reactants, more products Decrease of reactants Reverse reaction More reactants, less products Increase of products (same as decrease of reactants) Decrease of products (same as increase of reactants) __Temperature Changes__ __Action Increasing rate of: At the new Equilibrium State:__ Increasing temperature Endothermic reaction Less reactants, more products (of favoured// //reaction) Decreasing temperature Exothermic reaction Less reactants, more products (of favoured// //reaction) Decrease in Gas Volume Forward reaction Less reactants, more products (of forward// //reaction) __Action Increasing rate of: At the new__// //__Equilibrium__// //__State__////__:__ Increasing volume reaction producing less amount Less reactants, more products (of// //favoured reaction) Decreasing volume reaction producing more amount Less reactants, more products (of// //favoured reaction)//

(b) //Adding Catalysts Adding Inert Gases//

2. (a) H2O(l) + energy ↔ H2O­(g) The container is heated. (b) H2O(l) ↔ H+(aq) + OH-(aq) A few crystals of NaOH(s) are added to the container.

(c) CaCO3(s) + energy ↔ CaO(s) + CO2(g) CO2(g) is removed from the container.

(d) CH3COOH(aq) ↔ H+(aq) + CH3COO-(aq) A few drops of pure CH3COOH(l) are added to system 3. NH3(g) + 5O2(g) ↔ 4NO(g) + 6H2O(g) + energy (a) O2(g) is added to the system. //More concentration in the reactant side means increased rate of forward reaction, so there will be fewer reactants and more reactants in the newly established equilibrium.// (b) The temperature of the system is increased. //The reverse reaction is endothermic, so it is favoured. Therefore, there will be more reactants and less products in the newly established equilibrium.// (c) NO(g) is removed from the system. //Smaller concentration in the product side means decreased rate of reverse reaction, so there will be fewer reactants and more products in the newly established equilibrium.// (d) The pressure of the system is increased by decreasing the volume of the reaction vessel. //Since there are 6 moles of reactants per 10 moles of products, the reverse reaction is favoured, so there will be more reactants and fewer products in the newly established equilibrium.// (e) Argon gas is added to the system without changing the volume. //Since argon gas is inert, it increases the probability of successful collision of particles for both reactions, so there is no change to the system.// 4. CuCl42-(aq) + 4H2O(l) ↔ Cu(H2O)42+(aq) + 4Cl-(aq) dark green blue (a) Hydrochloric acid is added (increase in chloride ions) (b) Silver nitrate is added. (reacts with chloride ions to create silver chloride solid??) 5. Cr2O72-(aq) + H2O(l) ↔ 2CrO42-(aq) + 2H+(aq) orange yellow Because of the following reaction Cr2O72-(aq) + NaOH(aq) ↔ 2CrO42-(aq) + H+(aq) + Na+(aq), the rate of consumption f Cr2O72-(aq) increases, meaning the forward reaction dominates, meaning that at the new equilibrium state, there will be more yellow chromate ions. 6. C2H4(g) + H2(g) C2H6(g) + energy //A – volume of container increased. B – temperature increased. C – C2H6 added. D – no change E – C2H4 removed.//