Chemistry Equilibrium Lab

Quantitative Data

Data Processing

Graph 1.  Reaching equilibrium in 10mL of water in cylinder A and B with the same radius straw with 10mL of water and with 5mL of water added to cylinder A after results from Table 1.

Graph 2. Reaching equilibrium in 10mL of water in cylinder A and B with different radius straw with 10mL of water and with 5mL of water added to cylinder A after results from Table 1.

Conclusion

In experiment, the process where dynamic equilibrium is reached was simulated by the transfer of water by straws. When using two straws of the same radius as shown on Graph 1, we can see that dynamic equilibrium is reached as the volume of water in cylinder A decrease and the volume of water in cylinder B increases. In other words, the rate of the forward reaction slows while the rate of the reverse reaction increases until they are at equal rates. After the addition of 5.0 mL in cylinder A, using Le Chatelier’s principal it is possible to predict what will happen to the system. If concentration of the forward reaction increases, equilibrium move towards reverse reaction and will correct itself to re-establish equilibrium.  There was 10.0 mL of water in the previous reaction and dynamic equilibrium was reached when the volumes were 5.0 mL in each cylinder. When 5.0 mL were added to cylinder A the volume went back to 10mL. We can predict that 15.0mL in total will cause equilibrium to be reached at 7.5mL as the rate of transfer is still the same. When using different radius straws, it is noticeable that the rate of transfer will differ as the thicker straw can hold more water during each transfer.  Therefore the volumes in the respective cylinders will be different as the rates of reaction are not the same due to the different straws.  This can be seen on Graph 2. The volume in cylinder A decreases as the volume in cylinder B increases. The rates eventually become equal at equilibrium but at different volumes. In other words, dynamic equilibrium can still be reached to have equal forward and reverse rate if the concentration of the reactant and product are different.

1. In the same radius straw lab, the volume (analogous to concentration) of water in cylinder A decreased as cylinder B increases to reach equilibrium at 5mL. At equilibrium, the volumes or concentrations were the same and also the rate of transfer were also the same. In the different radius straw experiment the volume or concentration of water in cylinder A also decreases while cylinder B increased. They reached equilibrium at different concentrations but still having the same rate of transfer.

2. When 5mL of water was added to cylinder A the curve went back to the original 10mL for the same radius experiment and also jumped 5mL for the different radius experiment

3. The point where the two lines meet for both the same and different radius experiments means that the volumes at those points are equal. The first flat portion on the same radius straw graph is when the volumes and rates are equal and that equilibrium is reached with 10mL of water. The second flat portion is when equilibrium has been reached again with the additional 5mL. The first flat portion on the different radius straw graph is when the rate of transfer is equal but the volumes are different with 10mL of water and the second flat portion is with the added 5mL.

4. The additional 5mL of water in cylinder A of the same radius straw experiment results in an additional 2.5mL in cylinder B. The additional 5mL of water in cylinder A of the different radius straw experiment results in an additional 3.2 mL in cylinder B.

5. The system is referred to as “closed” because neither matter nor energy can be lost or gained. There is only water transfer between the two graduated cylinders by straw and is proceeding at a constant rate.

6.  The factor keeping the relative volumes constant during the experiment is the radius of the straws that keep the amount of water the straw can hold due to air pressure the same. The environment where the experiment is held in also controls the relative volumes of water because of the evaporation of water due to the temperature and the air pressure. Another control is the person that is doing the transferring of the water because they have the constant ability to use straws to transfer water.

Limitations

        There were many different errors of the experiment. The random errors included gunk at the bottom of the graduation cylinder that got stuck in the ends of the straws. Those ends were also flattening out because of the force that was applied to transfer water. The random errors could affect our results because of inaccurately and slow down the time required to reach equilibrium. Doing the lab on separate days altered the consistency of equipment used for the experiment. The human errors t of the experiment include parallax when reading the values of water on the graduated cylinder which could cause the graph of the experiment to also in inaccurate. In addition, our fingers might not be moist all the time to maximize suction of water in the straws. These errors could increase or decrease the number of transfers needed to reach equilibrium.

Improvements

        Improvements that could be made to this experiment include cleaning out the graduated cylinders beforehand and make sure that there are not any water droplets along the wall of the graduated cylinder so the volume of water would be accurate. We could also moisten our finger after every transfer of water to maximize the suction and volume of water with each transfer. A more careful reading of the graduated cylinder could avoid parallax and imprecise data.

More trials of this experiment and doing it in one day could have been done to improve the accuracy of the results.