Magnesium oxide lab report—Finishing up.
You’ve got your prelab portion and your data. Here’s what’s needed to finish up:
• Calculations section: You are to clearly calculate:
a) the empirical formula. Nothing is taken for granted as understood, you are to
explain each calculation you make. See the example from your hydrate lab:
We said what we were calculating, showed in words the data or equation that
would give that answer, we then substituted in our values complete with
units/labels, then finally wrote our answer, rounded to correct SF and labeled
with units. Here’s an example as it should’ve looked from that lab report:
Mass of CuSO4•XH2O = (Mass of dish + hydrate) – (Mass of empty dish)
= 78.22g – 73.12g = 5.10 g CuSO4•5H2O
See how it works? Your calculations will look the same, but what you’re
calculating is different. In your EF calcs, keep your units on to show what your
current unit is (grams, moles)
b) The percent error. We know the ratio is supposed to be 1:1, yes? I attempted
to explain what we’d compare (measured vs. accepted) in class, here’s a
slightly different way of saying the same thing.
Moles of magnesium
that we
moles of oxygen
measured vs. the accepted ratio. (We’re plugging in our values and dividing!)
If you measured 5.30 moles of Mg and 4.00 moles of O, your measured ratio
would be 5.30 ÷ 4.00 = 1.33. Just like the above calculations, you explain
! how it’ll be calculated in words, you
what youre calculating, you write
substitute, then you solve. No just cramming numbers on the page!
We are to compare the ratio
When you’re calculating using an equation, write the
equation, substitute, solve and box answer:
% error =
measured value - accepted value
" 100%
accepted value
45.12 g - 43.00 g
" 100%
43.00 g
= 4.9% error
=
!
With calculations completed, you now will write your conclusion. Follow the
format suggested on the 2nd half of your lab packet (Keep that for future
reference!) Key thought: Even though you just calculated your EF, your % error,
you still need to discuss/announce your findings. You restate these findings, in
words, here. For your paragraph on error analysis, you should give reasons for the
error that makes logical sense. It’s not that you screwed up, it’s just that it didn’t
come out ideally. In paragraph 3, explain how this lab helped your understanding
of the concepts covered in this lab. What clicked (if anything)? Did it work as
well as you hoped? Did you enjoy it? This is the one place in the report where you
can use the first person (“I” language)