Stoichiometry Lab
Analysis and Calculation
Stoich. Lab Introduction Part I
• You must incorporate in FULL SENTENCE FORM the
following:
• We have TWO purposes.
1.
2.
Determine the amount of precipitate produced in grams.
Determine the concentration of the sodium carbonate.
 Additional Topics:
– Describe the differences between quantitative and
qualitative data. Which are we using in this laboratory and
why?
– Describe volumetric and gravimetric analysis, give general
examples we used in the laboratory.
– Explain the filtration apparatus general purpose and its’
set-up.
Stoich. Lab Introduction Part II
• More Topics which MUST be discussed:
– Discuss the molarity formula: give the formula,
brief description of the variables, and the
purpose of molarity.
– Explain what are the purposes of molar
coefficients (the molar ratio).
– (WRITE THIS SENTENCE LAST)  Briefly in one
sentence, describe specific experiment.
Materials List & Procedures
• MATERIALS:
– In your materials, list those ONLY USED IN LAB.
– Draw the Filtration Apparatus AFTER the list of
materials with appropriate labels.
• PROCEDURES:
– Simply summarize all procedures as appropriate.
Data Table
• Your Data Table MUST include:
– Na2CO3 mL used
– CaCl2 mL used
– Weight of filter paper alone
– Weight of [filter paper + precipitate]
– Weight of precipitate alone
The Data Analysis of Stoich. Lab
• There are five parts to the Data Analysis section. You MUST include a
heading for each part. After the heading, you will show the
appropriate work.
1.
Identify the solid white precipitate
(What compound did we produce in lab?)
2.
Obtain the final weight of the white precipitate
(How much does it weigh & first purpose of lab)
3.
Convert to moles of the sodium carbonate
(with moles of sodium carbonate can determine the concentration)
4.
Calculate the molarity of the sodium carbonate
(The second purpose of the lab)
5.
Determine the percent Error for the Molarity
(How accurately did you perform the experiment?)
Part 1: Identify the white precipitate
• What is the predicted precipitate according to Solubility
Rules?
Basic Eq: SrCl2(aq) + Na2CO3(aq)  SrCO3(s) + 2NaCl(aq)
The precipitate will be, strontium carbonate.
Ionic Eq: MUST be in laboratory report
Net Ionic Eq: MUST be in laboratory report
Part 2 & 3 of Data Analysis Section
Part 2: The weight of the precipitate.
[filter paper + precipitate] – filter paper = precipitate (grams)
Part 3 : The moles of sodium carbonate
Use the Basic Eq: SrCl2(aq) + Na2CO3(aq)  SrCO3(s) + 2NaCl(aq)
obtained g SrCO3 x 1 mol SrCO3 x 1 mol Na2CO3 =
147.63 g SrCO3 1 mol SrCO3
Conversion Keys:
moles Na2CO3
1 mol of SrCO3 = 147.63 g SrCO3
1 mol SrCO3 = 1 mol Na2CO3
Part 4: Molarity of the sodium
carbonate
• To determine the molarity of the solution, we use:
M = mol of solute =
L of solution
mol of moles Na2CO3
L of solution
• Add the used Na2CO3 solution in mL, then convert to
Liters
• Apply liters of sodium carbonate and mol of sodium
carbonate back into the molarity formula:
Part 5: Percent Error
• Once determining the experimental Molarity
of Na2CO3, compare to expected value.
• Percent Error = 100 x Your Result – Accepted Value
Accepted Value
Review - Road Map for Stoich. Lab Survival
1&2
3
4
5
• Predict the Precipitate, convert to moles of precipitate
• Use Molar Ratio to obtain moles of sodium carbonate
• Add up how much sodium carbonate was used in the lab
• Apply the Molarity formula and find the Molarity of the
sodium carbonate
• Determine the Percent Error for the molarity!