Question

question 8 (1 point) saved
listen
what is the possible reason for a yield percent greater than 100% in this lab?
the collected copper was not completely dry in the oven.
reaction in the solution wasnt complete
copper was not collected completely and there was a loss of this product.
the amount of aluminum present was not enough and it became the limiting reagent in the reaction process.
question 9 (1 point)
listen
as the reaction proceeds, what should you do to the aluminum wire?
remove the wire every 2 minutes and wipe the copper off.
weigh the mass of the wire every 2 minutes.
leave the wire still and do not touch.
shake the wire continuously.

Explanation:

Question 8

If the collected copper was not completely dry, the measured mass (which is used in the percent - yield calculation: $\text{Percent Yield}=\frac{\text{Actual Yield}}{\text{Theoretical Yield}}\times100\%$) will be higher than the true mass of copper. This can lead to a percent yield greater than 100%.

• If the reaction wasn't complete (Option 2), the actual yield would be less than the theoretical yield, so percent yield would be less than 100%.
• If copper was not collected completely (Option 3), the actual yield would be less than the theoretical yield, so percent yield would be less than 100%.
• If aluminum was the limiting reagent (Option 4), it just means that the reaction would stop when aluminum is consumed, and it doesn't cause the actual yield to be greater than the theoretical yield.

• Removing the wire every 2 minutes and wiping the copper off (Option 1) would interfere with the reaction process. The copper that forms on the wire is part of the ongoing reaction, and removing it would disrupt the reaction kinetics.
• Weighing the mass of the wire every 2 minutes (Option 2) is not a standard procedure during the reaction. The reaction needs to proceed without constant interruption for weighing.
• Leaving the wire still and not touching (Option 3) is incorrect. Shaking the wire continuously (Option 4) helps to expose more of the aluminum surface to the reactants (assuming it is in a solution - based reaction). This increases the surface area for the reaction, allowing the reaction to proceed more efficiently.

Answer:

The collected copper was not completely dry in the oven.

Question 9