Examine the solution for any excess aluminum foil. The copper can form a thin fi

Question

Examine the solution for any excess aluminum foil. The copper can form a thin film and look like dull foil. Stir the solution with the glass rod and rinse rod with DI water into the beaker. If you have aluminum foil remaining, use tweezers or forceps to remove. Make sure you don't remove any of the copper precipitate. Use a disposable pipette to rinse the aluminum pieces back into the 50-mL beaker with water. Set up a Buchner funnel, a filter flask, and vacuum tubing connecting vacuum line (See Figure 10.2). Place a filter paper circle into the Buchner funnel and add a few drops of deionized water to wet the filter paper. Pour the mixture from the 50-mL beaker into the Buchner funnel. Use small amounts of water (about 2 mL, three times) to transfer all of the solid from the beaker into the funnel. Wash the copper two more times with small amounts of water (about 2 mL). Turn off the vacuum. Add 10 mL of ethanol to the solid copper on the filter paper. Let it sit for about one minute. Turn on the vacuum and filter the ethanol. Let the vacuum continue for about five minutes. Measure and record the mass of a clean, dry, watch glass. Transfer the dry copper solid to the watch glass. Measure and record the combined mass of the watch glass and copper solid. Repeat Steps 1 through 32 for a second measurement. In Procedure Steps 25 and 27, a student lost an amount of copper. Explain how that will impact the formula of the anhydrous copper chloride.

Explanation / Answer

When you lose copper during filtration or washing then the percent composition by mass will get reduced and it will
certainly give an error in the empirical formula. Mass measured after evaporation will change and hence it changes the
composition percent which is used to determine the empirical formula.

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