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Day 1 |
Day 2 |
Day 3 |
Lab |
Skills Test
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Sample Problem: calculate the formula mass of C2H5OH
Units must be included.
Day 2
Calculating percentage composition:
Research Links:
the sum of all the atomic masses in a formula.
To make these calculations easier, round all atomic mass numbers to the nearest whole number.
Set up your calculation this way:
C = 12 x 2 = 24
H = 1 x 6 = 6
O = 16 x 1 = 16
46 u
Your formula mass
calculations should
look like this.
The units of formula mass are "atomic mass units" - u
Make-Up Assignment 071:
This assignment must be turned in by the beginning of class tomorrow to receive credit.
Remember that you must show how chemistry problems are set up and the units of the answer.
the percentage of the formula mass represented by each element.
Percentage composition compares the mass of one part of a substance to the mass of the whole.
Do a formula mass calculation.
Divide the total atomic mass for each element by the total formula mass of the compound.
Example: Calculate the percentage composition of C2H5OH
The formula mass step
.
The percentage calculation step
Your % composition
calculations should
look like this.
C =
12 X 2
=
24
.
24 / 46
= 52% Carbon
H =
1 X 6
=
6
.
6 / 46 = 13% Hydrogen
O =
16 X 1
=
16
.
16 / 46
= 35% Oxygen
.
Total = 46 u
.
.
Because of rounding mass numbers to whole numbers, the total % could be between 99 and 101. If it is outside that range, you probably have a mistake.
Portfolio Assignment 072:
Scoring criteria
