what is the oxidation reaction for Ag + NaCl?

Analysis of Silver in an Alloy

Purpose: The purpose of this experiment is to determine the silver
content in a silver-copper alloy. Since neither silver nor copper are
very reactive this is first done by dissolving the alloy in nitric acid.
The acid oxidizes the metals producing Ag+ and Cu+2. The reduction
product is nitrogen monoxide which reacts with oxygen in the air to form
nitrogen dioxide. Once the silver and copper are in the solution they
can be separated by precipitating out the silver as silver chloride.
This insoluble solid can then be filtered out of the solution, dried and
massed.

Silver-Copper Alloy Nitric acid (HNO3), 6 M

Sodium Chloride Beakers, 100 and 250mL

Stirring Rod Watch Glass

Hot Plate Graduated Cylinder

Triple Beam Balance Wash Bottle

Tongs Fume Hood

Para film

Materials:

Procedure:

1. Obtain a sample of silver-allow and determine its mass precisely on
a balance.

2. Put the allow in a clean 100mL beaker and carefully pour 10 mL (for
ever .5g) of 6M nitric acid over it. Cover the beaker with the watch
glass. It may be necessary to heat the solution so the alloy totally
dissolves.

3. Calculate the amount of sodium chloride that would be necessary to
precipitate the silver in your sample assuming that it is 100% silver..
use a balance to weigh out 2X this amount. Dissolve this in
approximately 25mL of distilled water.

4. Remove the watch glass from the baker and rinse the bottom. Slowly
add the sodium chloride solution. Stir with a stirring rod and use
distilled water to rinse any solution clinging to the rod back into the
beaker.

5. Cover the beaker with Para film and allow it to stand overnight.

6. Prepare a funnel and a piece of filter paper (make sure to weight
the filter paper first). Also prepare a wash bottle with 150mL of
distilled water and 6M HNO3 to rinse the baker with as you filter.

7. Carefully pour the solution and precipitate into the filter. Be
sure to get every particle.

8. Leave the sample to dry overnight in a safe place. Once dry, weigh
the sample.

9. From your data determine the percent silver in the alloy.

Calculations:

Ag + NaCl → AgCl +Na

1. How much NaCl was used?

2. How much AgCl was produced?

3. What is the percent of silver in the dime?

4. What is the percent error of the lab?

Data Table:

Mass 1964 dime: 2.522g

HNO3 Added: 74mL HNO3

NaCl Added: 2.732g NaCl

Mass of Filter Paper: 1.309g

Mass of Filter Paper and AgCl: 7.309g

Reaction: Ag + NaCl → AgCl + Na

Amount of NaCl Used: 2.732g NaCl

Amount of AgCl Produced: 6.00g

Percent of Ag Produced:

Percent Error:



Discussion:

At first we tried to precipitate a 1964 nickel in order to find its
percent of silver. The solution did not change color when NaCl was
added, and after several days we realized that the solution was not
precipitating. The solution did not precipitate because a 1964 nickel
is solely composed of a 75-25 alloy. Because of this, we had to change
our experiment on a nickel to that of a dime.

During our experiment we doubled the amount of salt. This was done
because the salt is what caused the AgCl to precipitate, and we needed
to make sure that as much AgCl was precipitated as possible.

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ces of sodium could have been among the AgCl, causing our measurements
to be inaccurate. The triple-beam balance also could have added to
inaccurate weights of the paper and of the AgCl because the one we used
was fairly imprecise.