Lab E5 Flashcards
Is there a chemical reaction that goes to completion or complete?
Why?
No
Even when reaction stops, some reactants remain
When do chemical reaction reaches equilibrium?
If the concentrations of the reactants and products no longer change with time.
It describes the relative amounts of reactants and products that remain at the end of a chemical reaction.
It may shift if an external stress is applied
The stress may be in the form of a change in:
Position of Equilibrium
Equilibrium position of a reaction
Temperature
Pressure
Concentration of one of reactants or products
The response of a reaction at equilibrium to changes in conditions is summarized in
It states a perturbed from equilibrium shifts its equilibrium position to relieve the applied stress.
Le Châtelier’s principle
Causes a shift in equilibrium because all chemical changes involve either absorption (endothermic) or release (exothermic) of energy.
Temperature
As stress such as _____ the concentration of one side of the chemical equation (either reactant of product side) will favor the formation of that side of the equation while _____ the concentration will favor the formation of the opposite side.
decreasing
increasing
An increase in temperature favors the reaction in the endothermic reaction
Reversible reaction
Only _____ can change the value of the equilibrium constant.
Temperature
It affects only gaseous species and an increase in pressure (decrease in volume) will favor the reaction to produce less gas molecules
Change in pressure or volume
Good example for the study of equilibrium system
iron-thiocyanate
If the solution is initially reddish, the equilibrium shifts to the right, the solution becomes ______
While if the equilibrium shifts to the left, the solution becomes _______
darker red
light red or straw yellow
Experiment questions:
- Did all the experiments results agree with the expected or theoretical results? If not, what are the possible sources of errors.
- Do the results of the temperature variation indicate that the forward reaction is exothermic or endothermic? Is it the reaction reversible?
- If the change in color of bromothymol blue indicates the presence of carbonic acid, what do you conclude about the effect of pressure change on the position of equilibrium? Write the equilibrium of the reaction and explain.
