2/14/2013 Jennifer Lye, Sourabh Das, Katherine Chien Ms. Johnson

Which Factors Affect the Rates of Reaction the Most2AgNO3 (aq) + CuCl2 (aq) 2AgCl(s) + Cu(NO3)2 (aq)

Hypothesis:

1) Temperature: The increase of temperature will speed up the rate of reaction since the molecules have higher kinetic energy and thus will collide at a higher rate.

2) Concentration: A higher concentration means there are more molecules present to collide with thus there will be more collisions over a shorter period of time.

3) State: The addition of water to the copper chloride (going from a solid to an aqueous state) will allow for the copper and chloride ions to dissociate, therefore they will form new compounds more easily and thus speed up the reaction.

We hypothesize that temperature will have the most effect on the rate of reaction since higher temperature will give molecules more kinetic energy, in comparison, a higher concentration of solution has more molecules to collide with, but may not have enough energy to form the new product. The change in state would slow down the reaction rate since the solids need to be dissociated before they can react.

AgNO3 CuCl2

C = 0.1 mol/L C = 0.1 mol/L AgNO3 is the limiting reagent.

V = 10 mL v = 10 mL

N = 0.01 mol n = 0.01 mol

0.01 x ½ = 0.005 mol 0.01 x 1/1 = 0.01 mol

Materials:

Part 1)

100 mL beaker Filter paper Hot plate 2 – 100 mL graduated cylinders

Stop watch Goggles

2/14/2013 Jennifer Lye, Sourabh Das, Katherine Chien Ms. Johnson

100 mL of 0.1 mol/L AgNO3 (aq) 30 mL of 0.1 mol/L CuCl2 (aq)

Thermometer Beaker mat

Part 2)

100 mL beaker Filter paper 2 - 100mL graduated cylinders Stop watch Goggles 30 mL of 0.1mol/L AgNO3 (aq)

10 mL of 0.1 mol/L CuCl2 (aq) 10 mL of 0.2 mol/L CuCl2 (aq)

10 mL of 0.15 mol/L CuCl2 (aq)

Part 3)

100 mL beaker Filter paper 2 – 100 mL graduated cylinders Stop watch Goggles 30mL of 0.1mol/L AgNO3 (aq)

10 mL of 0.1 mol/L CuCl2 (aq) 2 g of anhydrous CuCl2 (s)

Scoopula

Procedure:

Part 1) - Temperature

1) Measure 10 mL of 0.10mol AgNO3 solution into a test tube2) Measure 10 mL of 0.10 mol CuCl2 solution in a graduated cylinder and heat to 30°C.3) Add the CuCl2 solution into the test tube and let it react for 1 minute 4) Filter the solution and measure the mass of precipitate (after it dries)5) Empty the beaker into the waste disposal unit and rinse6) Repeat step 1-5 for CuCl2 at 45˚C and 60oC using the hot plate to heat the solution

Part 2) – Concentration

1) Measure 10 mL of 0.10 mol AgNO3 solution into a test tube2) Measure 10 mL of 0.10 mol CuCl2 solution in a graduated cylinder 3) Add the CuCl2 solution into the test tube and let it react for 1 minute 4) Filter the solution and measure the mass of precipitate (after it dries)5) Empty the beaker into the waste disposal unit and rinse6) Repeat step 1-5 for 0.15 mol/L CuCl2 and 0.20 mol/L CuCl2

2/14/2013 Jennifer Lye, Sourabh Das, Katherine Chien Ms. Johnson

Part 3) – State

1) Measure 10 ml of AgNO3 into one of the graduated cylinders and pour into the first beaker2) Measure 1.34 g of CuCl2 (s) into the second beaker and add to the first beaker3) Add the anhydrous CuCl2 powder into the test tube and let it react for 1 minute4) Empty the beaker into the waste disposal unit and rinse5) Measure 10 ml of AgNO3 into one of the graduated cylinders and pour into the first beaker6) Measure 1.70 g of hydrated CuCl2 (s) into the second beaker and add to the first beaker7) Add the anhydrous CuCl2 powder into the test tube and let it react for 1 minute8) Measure 10 mL of 0.10 mol/L AgNO3 (aq) into its graduated cylinder and pour into the first beaker9) Measure 10 mL of 0.10 mol/L CuCl2 (aq) into the other graduated cylinder and add to the first

beaker10) Add the CuCl2 solution into the test tube and let it react for 1 minute 11) Empty the beaker into the waste disposal unit and rinse

* Make sure station is clear before returning to your desk *

Observations

Part 1) 0.1 mol CuCl2(aq) to 0.1mol AgNO3(aq)

Temperature ( ̊ C) Mass of ppt mmol mmol/min30 0.07 0.488 0.488/min45 0.14 0.977 0.977/min60 0.14 0.977 0.977/min

Part 2) CuCl2(aq) to AgNO3(aq) at room temperature

Concentration (mol/L) Mass of ppt mmol mmol/min0.10 0.02 0.140 0.140/min0.15 0.09 0.628 0.628/min0.20 0.15 1.047 1.047/min

Part 3) 0.1 mol CuCl2 to 0.1mol AgNO3 at room temperature

State Mass of ppt mmol mmol/minanhydrous 0.18g 1.256 1.256/min

solid (hydrated) 0.24g 1.675 1.675/minaqueous 0.12g 0.837 0.837/min

2/14/2013 Jennifer Lye, Sourabh Das, Katherine Chien Ms. Johnson

Analysis

Since the reaction was a fast one and the bulk of the reaction is finished under a minute, the temperature doesn't affect the quantity of AgCl produced after 45 degrees.

As can be seen from the Rate vs. Concentration graph, an increase in concentration has a linear increase in reaction rate. This shows the order of the reaction for CuCl2 is 1. As the slope is so steep, it can be seen that an increase in concentration has a large increase in reaction rate.

As the graph shows, the rate of reaction was highest during the hydrated CuCl2 reaction and lowest during the aqueous CuCl2 reaction, with the anhydrous reaction landing somewhere in the middle. Judging from the expectation that an aqueous solution will react faster due to the ions already being dissociated, it’s very strange that the aqueous reaction was the slowest. Analyzing our experimental design can lead to some possible sources of differentiation. When we look at the difference between the anhydrous and aqueous compounds, we notice that they contain the same amount of CuCl2 in moles. However, there is a lot more water in the aqueous solution. Now this is obvious, because we purposefully added water to the second compound to make it aqueous. But, there is still a difference. When we added the compounds to the AgNO3 solution, the water in that solution helped dissociate any ions in the CuCl2 it also increased the volume of liquid in the solution. In the anhydrous reaction however, there is less liquid in the reacting solution than in the aqueous reaction. This means that the chance that collisions will occur in the anhydrous reaction is a lot higher than in the aqueous solution, despite the aqueous reaction’s pre-dissociation.

Conclusion

The temperature and concentration both had significant effects on the reaction rate, however the greatest improvement in rate could be seen when hydrated CuCl2 as the reaction rate nearly doubled.

However many sources of error must be taken into account. Since there were only 3 data points, it was not very clear if a graph was linear or exponential as a slight error in one point would change the shape of the graph significantly. Another way this could have been improved was by making time the dependent variable. As each of our samples were filtered, the reactants continued to react even while it was being filtered as it took time for the solution to pass through the filter paper. This time was not accounted for. In the end, we had to dry the filter paper by heat. As the evaporating water led the dissociated CuCl2 to recombine, this lead to errors in the mass measured at the end as it was not the mass of pure AgCl. All these affected our final results and could be improved upon next time. The experiment could have also been improved by observing other numeric factors such as the concentration of AgNO3.