Pre-lab Assignment for Gravimetric Analysis Lab

1. What is gravimetric analysis? Describe this in your own words, don’t just copy something down

from Google. You should be able to explain it if asked. (Hint: You have already performed one

gravimetric analysis lab this year.)

2. a. If you are given a sample identified only as a Group I metal carbonate, what does that mean?

b. What is the metal to carbonate ratio of this sample?

c. What will happen to this sample if mixed with deionized water?

3. To determine the identity of your metal carbonate (You really just need the identity of the metal,

right?), what information do we need in order to make a comparison to the average atomic mass

provided on the periodic table?

4. To identify the element (or compound) using the molar mass, we need to know the mass of the

metal carbonate and the # of moles.

a. How can we determine the mass of the unknown Group I metal carbonate?

b. How can we determine the number of moles of the unknown Group I metal carbonate?

(Consider your answer to #2)

5. a. If the Group I metal carbonate is soluble in water, what can you do experimentally to determine

the number of moles of one of the ions in the sample?

b. What will happen to the carbonate if you add a solution that contains an alkaline earth metal?

c. Considering the answer to 5b, what type of reaction would you perform to determine the

number of moles of one of the ions?

d. Will you be able to measure the number of moles directly? If not, what will you measure after

this reaction that will allow you to determine the number of moles?

e. What ionic compound would you choose to react with the unknown Group I metal carbonate to

perform this reaction? Why? (Some groups may have different answers.)

f. Write a balanced equation for the reaction you described in part e.

6. As a general guideline, your experiment should look something like this:

Precisely measure the mass of an unknown Group I metal carbonate.

Dissolve in DI H2O

React with an ionic compound to precipitate the carbonate

Measure the mass of the NEW carbonate product and calculate the number of moles of

NEW carbonate.

Relate the number of moles of new carbonate product to the number of moles of original

carbonate product.

Calculate molar mass of the original Group I metal carbonate.

Deduce the identity of the original metal I carbonate.

Write your own DETAILED procedure for the gravimetric analysis of a Group I metal Carbonate.

(Hint: This time you ARE giving someone else instructions.

7. Include an anlysis of possible error that may be found in your procedure and what you plan to do

to prevent/minimize/eliminate them while performing the experiment.