# Magnesium oxide lab report—Finishing up ```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 &divide; 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
&quot; 100%
accepted value
45.12 g - 43.00 g
&quot; 100%
43.00 g
= 4.9% error
=
!