Download Lab 7: Moles of Chalk Lab

Lab 7: Moles of Chalk Lab
Introduction: Because atoms are so small, we would need really larger numbers to count them. Working with
really big numbers can be frustrating. Because of this, in chemistry we have a unit called a “mole”. A mole of
atoms means 6.02 x 10 23 atoms. (Similar to how a dozen donuts means 12 donuts).
Purpose:
Materials:
To determine the number of moles of chalk are used to write your name.
Piece of chalk
Electronic Scale
Procedure:
1. Obtain a piece of chalk.
2. Measure and record the mass of your chalk using the balance in the back of the room.
3. Write your full name on a piece of black construction paper.
4. After writing your name, mass the piece of chalk on the balance and record below.
5. If the mass doesn’t change, write your name until the mass changes!
Data:
A
B
C
Mass of chalk before writing your
name (g)
Mass of chalk after writing your
name (g)
Grams of chalk required to write
your name (g) (A – B)
Questions (Calculations):
1. Chalk is comprised primarily of Calcium Carbonate. The formula for Calcium Carbonate is CaCO3.
Calculate the molar mass of CaCO3 below.
2. We can convert the grams of a certain substance to the amount of moles of a certain substance using a
conversion factor (just like with currency!). In this conversion we know that we have grams of CaCO3
and we want moles of CaCO3. Since this is known, our conversion factor should look like:
æ C# Want ö
Grams of CaCO 3 ç
÷ = Moles of CaCO 3
è C# Have ø
Therefore, we just need to know what we want and what we have. The molar mass tells us what we
want and what we have! We know that 1 mole of CaCO3 = Molar Mass of CaCO3. Therefore, we
can plug this in to the equation above. Calculate the moles of chalk in your name using the equation
above.
LABS