This link might help you!!
https://www.eiu.edu/biology/bio1500/writing_a_lab_report.pdf
Answer:
1.375%
Explanation:
Percent Error = measured value - accepted value/ accepted value x 100
Measured Value: 15.78
Accepted Value: 16.00
Work:
* 100
* 100 = -1.375
You cannot have a negative percentage. Therefore the answer is 1.375%
The percent of O in Cr₂O₃ : 31.58%
<h3>Further explanation</h3>
Given
Cr = 52.00 amu, O = 16.00 amu
Required
The percent of O
Solution
MW Cr₂O₃ = 2 x Ar Cr + 3 x Ar O
MW Cr₂O₃ = 2.52+3.16
MW Cr₂O₃ =152 amu

First, lets balance the reaction equation:
4Fe + 3O₂ → 2Fe₂O₃
It is visible form the equation that 4 moles of Fe require 3 moles of O₂
Molar ratio Fe/O₂ = 4/3 = 1.33
Molar ratio O₂/Fe = 3/4 = 0.75
Now, we check the molar ratios present:
Fe/O₂ = 6.8/8.9 = 0.76
O₂/Fe = 1.31
Thus, Iron is the limiting reactant because its ratio is not being fulfilled while the ratio of O₂ is surpassed.