Equilibrium by Jesse

The point in time when both the product’s and reactant’s concentration are no longer changing.

Summary

Equilibrium occurs in reversible reactions when the concentrations of the product and reactant are no longer changing. In a reversible reaction the product will turn back into the reactant so the reaction becomes a continuous cycle.

During a reversible reaction there is a certain percentage of the reactant of the product that reacts each ‘step’. That percentage of the reactant is subtracted from the previous amount of the reactant and added on to the previous amount of product, this is called the the change forward. It is the same for the product; that percentage of the product is subtracted from the product and added on to the reactant. Once equilibrium occurs the change forward and the change reverse become the same and no longer change.

Facts

Equilibrium only occurs in reversible reactions because it is the only type of reaction that some of the product can and will turn back into the reactant.

The reaction never actually stops but since the change forward and change reverse become the same the amount of the product and reactant do not change and equilibrium is reached.

Change in temperature and pressure will cause a change in equilibrium and therefore change the concentrations of the products and/or reactants.

Visual

Here is a table to help your understanding.

The “certain percentages” are 60% of the reactant and 20% of the product

In the 1st step 60% of 10 equals 6 and 20% of 0 is 0. The equation for the reactant will be 10 - 6 + 0 = 4 and for the product 0 + 6 - 0 = 6. The next step 4 and 6 will be used at the start instead of 10 and 0.

Equilibrium is reached at step 5.

		60%	20%
		Reactant	Product
1st Step	Starting Amount	10	0
	Change Forward	-6	+6
	Change Reverse	+0	-0
	End	=4	=6
2nd Step	Change Forward	-2.4	+2.4
	Change Reverse	+1.2	-1.2
	End	=2.8	=7.2
3rd Step	Change Forward	-1.68	+1.68
	Change Reverse	+1.44	-1.44
	End	=2.56	=7.44
4th Step	Change Forward	-1.54	+1.54
	Change Reverse	+1.49	-1.49
	End	=2.5	=7.5
5th Step	Change Forward	-1.5	+1.5
	Change Reverse	+1.5	-1.5
	End	=2.5	=7.5
6th Step	Change Forward	-1.5	+1.5
	Change Reverse	+1.5	-1.5
	End	=2.5	=7.5

Importance

            The system that transports and delivers oxygen in the body depends on the reversable reaction, and equilibrium, between the oxygen and the hemoglobin in the blood. Most of the oxygen gets bonded with the hemoglobin molecules. The hemoglobin then carries the oxygen to the body tissues.

Question

How/why does temperature and pressure affect equilibrium?