Finalizing your Mg/H2 Lab Report:
Your Prelab is the first half of your report. See the other Word doc if you were unclear of
what is expected.
You are to continue on from your prelab. It ended with sections on Procedure and
Safety… Contiue from that point:
• Prelab Questions: Show all work, use complete sentences, make it perfectly clear both
what you are answering/calculating. If I can’t tell what you’re answering without looking
at the original question, you’ll be getting points docked.
• Data: Recopy Data tables from the lab booklet, including all your measured data. These
tables must be neat (either printed or drawn using a straight-edge to make the tables.
• Analysis: This section follows the format and information asked under the booklet’s
“Calculations” section. MAKE SURE to “announce” what you are calculating before
throwing down all your numbers; I want it to be clear what you are attempting to
calculate. For example, you should write Theoretical Yield of Hydrogen Gas before
your first calculation. Since we only did one trial, you don’t need to worry about the
average of your % yields as it’s the same as your % yield for the one trial you did! Show
all work clearly, write out the “bare-bones” equations before substituting in your data
values, make everything super-clear. Use sig figs—We got out the awesome balance so
you’d have 3SF in your mass rather than the 1SF you’d have if we only used the 0.01 g
balances we usually do. Make sure to keep up the SF quality!
• Post-Lab Questions: As with the prelab Q’s, be ultra-clear, make sure you either
rewrite the Q’s out or write complete sentence answers that make the original question
clear. Show any calculation work clearly and neatly. Remember, for post-lab Q #2, you
can calculate the needed volume of the 12M HCl solution by remembering that 12M
12 moles HCl
means
: This is a conversion factor that you can use to find out how many
1 L HCl
liters (and then mL) of HCl you’d need to react with your original specimen of Mg metal,
using stoichiometry. This volume is not the volume of gas at STP, but instead is the
volume of a solution! The molarity (M) tells us the number of moles per liter of the
 solution.
• Conclusion: Paragraph 1: What did you find? Look back at your objective and restate
the findings of your lab. Use complete sentences and be clear and correct.
Paragraph 2: Error analysis: Don’t just say “I could’ve measured wrong,” I want
thoughtful error analysis. Did you get 102% yield? Or 87% yield? I want you to explain,
logically, how that error could be explained. Remember our starting points: Why did we
use steel wool? How do fish breathe? –Use these thoughts and/or others to explain error.
Errors aren’t random either: Look at your calculations to figure out how a certain error
would’ve impacted your actual yield, or your theoretical yield, and explain how your %
yield will be impacted as a result.