Stoichiometry Lab

40 points

Purpose: To use your knowledge of stoichiometry equations to predict the amount of salt which will be produced from this reaction:

Baking Soda (NaHCO₃) + Hydrochloric Acid (HCl) -----> Salt + Water + Carbon Dioxide (CO₂)

Materials: Baking soda, 6 M HCl, Micropipettes, Watch Glass, Evaporating dish, goggles, hot plates

Procedure:

1. Measure and record the mass of the Watch Glass and Evaporating Dish to

the nearest one hundredth of a gram (0.01g). Mass of Empty WG and ED

2. Add between 2.00 and 4.00 g of baking soda to your E.D.

3. Take the mass of the W.G. and E.D. with the baking soda in it and record it to

the nearest one hundredth of a gram (0.01g). Mass of W.G., E.D., and

Baking Soda Subtract to find Mass of Baking Soda by itself.

4. Cover the E.D. with the W.G. and add hydrochloric acid SLOWLY to your

E.D. using your micropipette. This will start the reaction. You will see fizzing.

Be Careful not to breathe the fumes!

5. When the fizzing stops, you are done. This means you have added enough

HCl to make the reaction go to completion. What is left in your E.D. is the

products of the reaction (Do you know what they are?)

6. When you have finished, put the W.G. and the E.D. on top of hot plate in the fume hood

7. When the solution has all boiled away, and only a white powder remains,

remove the W.G. and E.D. from the hot plate. You can weigh it after it cools.

8. Take the mass of the cooled W.G. and E.D.. Record it to the nearest (0.01g)

as Mass of W.G./E.D. with NaCl residue

Calculations:

1. Using the mass of Baking soda (NaHCO₃), determine the mass of NaCl that

should be produced by this reaction. To do this, you will need to show a

balanced equation of this reaction and carry out the stoichiometry process.

Record your data on the data table to the nearest (0.01g) as Predicted mass

of NaCl residue.

2. Once you determine the real amount of NaCl produed from this reaction,

subtract it from your Predicted mass of NaCl residue and record this as

Difference between Predicted and Actual masses of NaCl on your

data table.

3. Determine the percentage error on your data table.

Questions:

1. What are the two reactants in this experiment?

2. What are the three products in this experiment?

3. Explain how you were able to isolate NaCl in the tube alone so you could

measure it? (In other words, how did you get rid of the Carbon Dioxide and

Water?)

4. Why did you have to make sure the whole W.G. and E.D. were dry before

weighing it?

5. If your experimental mass of NaCl residue was more than 1.00g more or less

than your predicted mass of NaCl residue, what possible explanation can you

offer for why this occurred?

6. Let us say, for the sake of argument, that it took 10.0 mL of the 6.00 M solution of HCl to

completely dissolve the baking soda. How many moles of HCl did you use on that baking soda?

7. That 6.00 M solution of HCl you used for this experiment was made from a stock solution of

12.0 M. Let us say that you wanted to make 100.0 mL of this 6.00 M HCl solution. How many

mL of 12.0 M HCl would you add and how much pure water would you add? (This is a molarity

from stock solution problem). Make sure you show your work. You can obviously figure out this

answer in your head, but you need to show your work for credit.).

Data Table

#1 #2 #3

Mass of Empty WG and ED

Mass of W.G., E.D., and

Baking Soda

Mass of Baking Soda

Mass of W.G./E.D. with

NaCl residue

Mass of NaCl residue

Predicted mass of NaCl

Residue

Difference between Predicted

and Actual masses of NaCl

*Percentage Error

*Remember % error = êpredicted mass – actual mass ê x 100

predicted mass

What is due for this lab? Please put them in this order. Neatness counts!

1. Calculations – show your work! Make sure that you separate trial 1, trial 2 and trial 3 calculations. In other words, you should do all three calculations for trial 1 TOGETHER, then for trial 2 TOGETHER and then for trial 3 TOGETHER. Label your calculations Trial 1, Trial 2 and Trial 3.

2. Questions – yes, you must copy the questions and then answer them.

3. Data Table – Nice and neat