Effect of temperature, concentration, and pressure on equilibrium
Our ongoing discussion has been on systems at dynamic equilibrium: for a reversible reaction, the rate of the forward reaction is equal to the rate of the reverse reaction. What happens if equilibrium is disturbed?
In this lab activity, we are going to examine the effect of changing reaction conditions on the position of equilibrium.
Part I: Effect of temperature
We will consider the equilibrium system
[Co(H2O)]2+(aq) + 4Cl-(aq) ↔ [CoCl4]2- + 6 H2O(l) pink blue
The forward reaction is endothermic.
3 test tubes
Test tube rack
Solid cobalt chloride
Hot water bath
10 ml graduated cylinder (for concentrated HCl)
1.Label the test tubes 1-3.
2.Add 0.5g solid cobalt chloride to each test tube.
3.To test tube 1, add 4ml concentrated HCl. Use the graduated cylinder to transfer the acid. This will be your first control sample. What is the color of your sample? __________
4.To test tube 2, add 4 ml distilled water. This will be your second control sample. What is the color of your sample? __________
5.To test tube 3, add ~1ml distilled water and ~3ml concentrated HCl. What is the color of your sample? __________
6.Place test tube 3 in the ice bath for 5 min or until there is a clear color change, whichever occurs first. What is the color of your sample? What is the shift in equilibrium? Explain your answers in terms of the reversible reaction.
7.Remove test tube 3 from the