Mountains into Molehills
Mass-Mole Conversions
Chem Catalyst

Arsenic, As, arsenic (III) oxide, As2O3,
and arsenic (III) sulfide, As2S3, are all
toxic because they contain arsenic.
a. Which is more toxic, 1 mol of As or 1 mol of
As2O3? Explain your thinking.
b. Which is more toxic, 1 g of As2O3 or 1 g of
As2S3? Explain.
Activity
Tape the questions to your left-hand
page
 Answer the questions on the righthand page.
 Tape tables onto the right hand page
in the appropriate place in the
question sequence.

Homework
Toxins Lesson 11: Mountains into
Molehills
 Pages 392-394
 Questions 3-8

Discussion


Why is it important to be able to convert back
and forth between mass and number of moles?
Using Dimensional Analysis to convert:
6.02 x 1023 items
1 mole
=
6.02 x 1023 items
1 mole
X grams
1 mole
1 mole
=
X grams
Practice Using Dimensional Analysis
1. How many moles of As in a sample with a mass of
125 g?
2. What is the mass in grams of 3.0 moles of Mg?
3. How many moles of CaCl2 are in a sample with a
mass of 10g?
4. What is the mass of a 0.16 mole sample of Cl2?
5. How many molecules are in 0.0583 moles of H2O?
6. How many molecules are in a 35 gram sample of
H2O?
Gas Molar Volume

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Can you measure the mass of a gas easily?
What is the volume of one mole of a gas? Check
your Lesson 10, What’s in a Mole, table.
Do you think this is always true for every gas?
Standard temperature = 273 degrees Kelvin (what is
this in Celsius?)
Standard pressure = 1 atmophere (atm) (= 14.7
lb/in2)
STP = 273 deg K and 1 atm
All gasses occupy 22.4 Liters at STP
Gas Conversions
22.4 Liters
1 mole
=
1 mole
22.4 Liters
1. What is the volume of 2.5 moles of oxygen
gas (O2) at STP?
2. How many moles of CH4 gas is in 0.4 Liters
at STP?
3. How many grams of N2 gas is in 6.8 Liters at
STP?
The Mole House

In the Mole House, in order to get to any other
room, you must pass through the “Moles Room”.
Sample Problems

On whiteboard