Percent Yield Lab Review

Common Mistakes and

Tips for Improvement

Overall

Organization & NeatnessTitle – appropriate and describes the lab

Correct Order

Headings

Organized Calculations

Written in third person

Introduction

Describe the reaction (double displacement)

- how do you know?

- use what you’ve learned to describe the reaction.

WRITE the chemical equation*

What will you be doing in the lab?

Calculating Percent Yield - Give a brief outline of how you will do that. What information do you need to gather from the lab?

Do not summarize results!! (=Abstract)

Materials List

Missing sizes of equipment (beakers and Erlenmeyer flasks)

Include quantities of chemicals required

Safety

Do some research

Personal Protective Clothing

WHMIS labels and safe handling ie. What to do about spills? Washing hands

after the experiment. Etc.

Disposal*

MSDS – You can find the MSDS for each of the chemicals to see the above information. If you cannot find it, come see me.

Procedure

For a formal lab report - write the procedure in PAST TENSE

When planning - write in present tense **Not enough detail (especially if someone

were to replicate the lab). Hard to follow. Some steps are too long – break it down

into simpler terms Stating sizes of equipment being used *Don’t forget to include apparatus set up

Data/Observations

Since there weren’t any trials conducted there would be no need for a large, formal data table

BUT organize the information – create a simple table for the data you will be measuring and need to make note of during the lab

Example:

Material Mass (g)

CuSO4 (s)

Zn (s)

Filter Paper

Filter Paper + Products

***DO NOT INCLUDE ANY TYPE OF CALCULATION IN YOUR DATA TABLE (except for averages if required)

Include a title (Table 1:___)

Qualitative Observations

Make sure it is organized

Make a table or use headings

Example:

Before Reaction: --

During Reaction: --

After Reaction: --

Include a title (Table 2:___)

Point form is sufficient – and easier to follow

Calculations:

Should be organized, neat, and easy to follow.

Include formulas and units

In order to calculate percent yield, first need to calculate the mass of JUST the product produced.

Calculations continued:

1. Calculate the mass of product produced *

2. Calculate the moles available of each reactant

3. Determine the limiting reactant

4. Determine the theoretical mass of product that should be produced

5. Calculate the percent yield

Analysis: Point of this lab was to calculate percent yield and to

see if the changes in your procedure/lab technique would improve your percentage yield!

DISCUSS your results

What do your results mean? What concepts of chemistry have you learned or can you research to explain why you got those results?

What does it mean to have a percent yield greater than or lower than 100%?

Any reasons why the mass of product produced was so high or so low?

Did the changes you made to your procedure improve your percentage yield? Why or why not?

Question #1 & 2 – the calculations were in the section above. You just need to discuss these questions in your analysis. Leave it in paragraph format. Mention limiting/excess/what the product is etc...This is all part of DISCUSSING YOUR RESULTS.

Conclusion

discuss at least 3 sources of error and improvement to these errors (this answers Q3). Be specific on errors that would affect the % yield.

Focus on equipment and procedure and not human error. You can mention human error if something went particularly badly.

This is also where you would mention any problems you had with the procedure you created. What worked or didn’t. Did they affect your results? How?