Mole Lab - DR. SANDE'S SCIENCE COURSES



Name: _____________________________ Hr: ____

Understanding the Mole

Introduction:

The relative mass of an object is how many times more massive the object is than a standard object. The atomic masses of atoms are all relative masses. They can be considered relative to any particular element. Historically, both oxygen and carbon have served as the reference standard. For our purposes we can also consider atomic masses relative to the least massive element – hydrogen, with an atomic mass of approximately one. Fluorine, with a relative mass of 19, is 19 times more massive than hydrogen. In this laboratory exercise you deal with the relative masses of beans. Then you will be asked to draw a parallel to the atomic masses of elements. In this lab the word “bean” can refer to any of the things we’re using – rice, bean, or lentil.

Purpose:

To develop an understanding of the mole concept and molar masses of elements through an analogy with a model system.

Safety:

Just don’t spill the beans!!!

Procedure:

***Be sure to use the same balance for the entire activity!

1. Count out exactly 100 beans of one type. Do not use any beans that differ greatly from an average bean. If you fail to do this, your results will not be accurate.

2. Put a paper cup on the electronic balance. Press the tare (zero) button.

3. Add the 100 beans to the paper cup and record their mass in the data table.

4. Repeat for the remaining types of beans.

Calculations:

5. Calculate the mass of one bean of each type and record the value in the data table in the Average Mass of one bean column. (Note: “Calculate” means to take the total mass of 100 beans and divide by 100 rather than weighing one particular bean.)

6. Determine the relative mass of each type of bean:

Relative mass = (average mass of one bean) / (average mass of the lightest type of bean)

7. Calculate the number of beans in one relative mass of each bean:

Number of beans in a relative mass = (one relative mass) / (average mass of one bean)

8. Check your calculated results in Step 7 by following these steps:

a. Place the paper cup on the balance pan and press the tare (zero) button

b. Add beans of your type until the balance contains the relative mass of your type of bean

c. Count the beans in one relative mass. Record this as the measured number of beans in one relative mass

d. Pour the beans into a pile. Retain your separate piles of relative masses of beans. You will answer questions about them later.

Part 1 – Bean Data Table

|Element |Mass of 100 beans |Average Mass of one bean |Relative Mass |Number of beans in a Relative Mass |

| | | | |Calculated |Measured |

|Rice | | | | | |

|White Bean | | | | | |

|Brown Bean | | | | | |

|Black Bean | | | | | |

Part 1 – Bean Data Table Questions

9. What did you find out about the number of beans in one relative mass?

[ ] same [ ] different

10. How do your calculated values compare to your measured values?

[ ] same (within one bean) [ ] different

11. Compare the volume of the relative mass piles.

[ ] same [ ] different Why? ________________________________________

12. a) What is the average mass of the lightest bean? ______________ g

b) What is the relative mass of the lightest bean? _______________ g

13. Among the elements, hydrogen has the least massive atoms. An atom of hydrogen has an average mass of 1.66 x 10-24g. This is very small, but remember it is only one atom! What is the relative mass of hydrogen if it is the least massive element? _________ g

Part 2 – Element Data Table

You are now going to apply the concepts you learned using the beans to actual atoms. In the data table below, the average mass of an individual atom, the relative mass of each element, and the number of atoms in a relative mass are given to you for five different elements.

*Look up the atomic mass of each element on a periodic table and record it in the table below.

|Element |Average mass of one |Relative Mass |Number of atoms in a Relative Mass |Atomic Mass |

| |atom |(grams) |(atoms) | |

| |(grams) | | | |

|Hydrogen |1.66 x 10-24g | | | |

|Helium |6.64 x 10-24g | | | |

|Carbon |1.99 x 10-23g | | | |

|Aluminum |4.48 x 10-23g | | | |

|Gold |3.27 x 10-22g | | | |

Part 2 – Element Data Table Questions

14. How do the atomic masses found on the periodic table compare to the relative masses you calculated?

[ ] same [ ] different

15. What did you find out about the number of atoms of each element in one relative mass?

[ ] same [ ] different

16. One relative mass of an element (measured in grams) contains how many atoms?

Hint: this number of atoms is known as a mole

17. How many atoms are in one mole or uranium atoms?

18. How many grams are in one mole of uranium atoms?

19. If you had 2.5 moles of gold, how many grams would you have and how many atoms would be there?

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