Dozens to Moles

Purpose: This lesson is an introduction to the concept of the Mole and calculating conversions related to the mole. The best analogy for understanding the mole is the dozen. Students intuitively understand a dozen is equal to the number 12, and that the weight (mass) of a dozen will depend on what you have a dozen of. Students will therefore start by calculating mass to dozen relationships and then progress to mass to mole relationships.

 

Background: Students need to be familiar with the conversion factor method of solving problems and understand the importance of keeping track of the units in a calculation.

 

Procedures:

  1. Students should complete the "Calculating Dozens" section first. Be sure to use the abbreviations for the balls provided. They are intended to mimic element symbols and make the look of your calculations similar to those you will do later with moles. If you are not sure how to set up a problem review the conversion factor method and example.
  2. After completing the read the "Dozens to Moles" section.
  3. Finally complete the "Mole Problems".

 

 

Calculating Dozens

Use the following equalities to calculate the questions below:

1 doz. Basketballs (Bb) = 2.21 x 103 g

1 doz. Soccer balls (Sb) = 1.44 x 103 g

1 doz. Tennis balls (Tb) = 5.76 x 102 g

1 doz. Ping-Pong balls (Pb) = 2.94 x 101 g

 

Questions: (example)

 

1. What is the mass of 2.3 doz. soccer balls?

2. Given a mass of 5.00 x 104 g of tennis balls, how many dozen tennis balls would you have?

3. 200 ping pong balls will have what mass?

4. 10.0 kg of basketballs is equal to how many basketballs?

5. A combiball is made of 1 basketball and 2 soccer balls. What is the mass of 3.6 doz. combiballs (BbSb2)?

6. A bunchball (BbSbTb3Pb10) is made of 1 basketball, 1 soccer ball, 3 tennis balls, and 10 ping pong balls. If you had a mass of 200. kg of bunchballs, how many dozen bunchballs would you have?

 

Answers

 

Dozens to Moles

 

How many is a dozen? (obviously 1 dozen = 12)

How much does a dozen weigh? (also obviously it depends on a dozen of what?)

 

 

A dozen is a number that has been given a name. The same can be said for a mole. The only difference is that the number defined as one mole is quite large.

 

1 mole = 6.022 x 1023

 

How many is a mole? (like 1 dozen = 12, 1 mole = 6.022 x 1023)

 

How much does a mole weigh? (like a dozen, the weight of a mole depends on what it is a mole of)

 

Where do you find how much a mole of something weighs?

Ca = 40.08 g/mol x 1 = 40.08 g/mol

N = 14.007 g/mol x 2 = 28.014 g/mol

O = 15.999 g/mol x 6 = 95.994 g/mol

1 mole Ca(NO3)2 =164.09 g (rounded to correct significant figures)

 

 

Mole Problems

 
  1. Find the mass of 1.34 mol of CaCl2.
  2. A bottle contains 45.3 g of KNO3. How many moles of KNO3 are in the bottle?
  3. How many molecules of H2O are in 0.583 mol of H2O?
  4. Given 4.14 x 1023 formula units of Na2SO4. How many moles of Na2SO4 would you have?
  5. From the above problem, what mass of Na2SO4 would you have?
  6. How many molecules of P2O5 are in 25.3 g of P2O5?

 

Answers

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