______ / 10 pts.
Name _______________________________
Class ______ Date _____________________
7.2 Making Salt Lab
Background
When an acid and a base are mixed in equal amounts the products of the reaction are salt and water. In
this experiment we will mix baking soda (NaHCO3) with hydrochloric acid (HCl) and produce sodium
chloride. Using stoichiometric calculations, the theoretical yield for the reaction can be predicted. After
running the experiment the actual yield of sodium chloride will be measured and the percent yield for
the reaction can be calculated.
Question
How does the experimental yield of sodium chloride compare with the calculated theoretical yield?
Materials
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Goggles and apron
Clean dry test tubes
Test tube rack
Lab burner
Scale
Test tube holder
Micropipettes
NaHCO3 (baking soda)
3M HCl
Safety Precautions
In this lab we must be very careful. Hydrochloric acid is a corrosive solution. If at any time during the
lab you get acid on yourself, wash it off immediately with soap and water and inform the teacher.
Goggles and an apron must be worn at all times.
Procedure and Observations
Procedure
1. Obtain a clean dry test tube.
2.
Measure and record the mass of
the test tube in the data table.
3.
Add enough baking soda to fill the
curved bottom of the test tube.
4.
Measure and record the mass of
the test tube and baking soda.
5.
Determine the mass of the baking
soda in the test tube. You want to
use between .25 and .50 grams of
baking soda.
Observation: Trial 1
Observation: Trial 2
Procedure
6. CAREFULLY add 3M HCl one drop
at a time, allowing the drop to run
down the inside of the test tube.
With the addition of each drop
swirl the contents of the test tube.
If any of your mixture bubble out
of the tube you must start over.
7.
Continue adding HCl until the
reaction ceases to occur.
8.
Evaporate off the fluid in the test
tube by gently heating the test
tube above a lab burner. If any of
the liquid is expelled from the test
tube you must start over.
Observations Trial 1
Observations Trial 2
9.
When it appears that the liquid
had completely evaporated,
remove the tube from the flame
and invert a clean dry test tube
above the opening of the test
tube. If any moisture collects
inside the inverted test tube,
continue heating until all moisture
is gone.
10. When the test tube is cool enough
to touch. Measure the mass of the
tube with its contents and record
it in the data table. Repeat steps
1-10 for two more samples.
Data Table
Trial 1
Mass of test tube. (g)
Mass of test tube and
baking soda. (g)
Mass of baking soda. (g)
Mass of test tube and
sodium chloride. (g)
Mass of sodium chloride.
(g)
Trial 2
Analysis and Calculations
1.
Write a balanced chemical equation for the reaction between sodium bicarbonate (baking soda) and
hydrochloric acid. (Your products are carbon dioxide, water, and sodium chloride)
2.
Calculate the number of moles of baking soda used in each trial.
a. Trial 1
b.
3.
Calculate the number of moles of sodium chloride produced in each trial.
a. Trial 1
b.
4.
Trial 2
How many grams of sodium chloride should have been produced in each trial based upon your
stoichiometric calculation? (Hint: Convert grams of baking soda to moles and use the mole ratio of baking
soda to sodium chloride in the reaction. Then convert to mass of sodium chloride.)
a. Trial 1
b.
5.
Trial 2
Trial 2
What was the percent yield for each trial? (actual/theoretical x 100%)
a. Trial 1
b.
Trial 2
Questions
1.
What was the gas produced in the experiment?
2.
How do the predicted amounts of sodium chloride compare to actual amounts produced? Did your
methods produce consistent outcomes?
3.
If all the water had not been removed from your product, how would that affect your final measurements
and calculations?
4.
Review the observations you made during the lab and identify any errors in the procedural methods that
you feel caused you not to get the exact grams of NaCl calculated for your theoretical yield. What might
be done to increase the percent yield?
More Practice with Stoichiometry
1. Given the following unbalanced chemical reaction:
___Na2S2O3 + ___AgBr  ___NaBr + ___Na3[Ag(S2O3)2]
a. How many moles of sodium thiosulfate are needed to react completely with the silver
bromide?
b. What is the mass of sodium bromide that will be produced using 42.7 grams of silver
bromide?
2. Given the following unbalanced chemical reaction:
___ B2H6 + ___O2  ___HBO2 + ___H2O
a. What mass of oxygen gas is needed to completely burn 36.1 grams of diboron
hexahydride?
b. You burn 19.2 grams of diboron hexahydride and are able to collect 15.7 grams of
water. What is your percent yield?