Lab Activity No. 2 UNDERSTANDING THE MOLE
OBJECTIVE: In this activity you will devise a means of answering the following questions: 1. How many marbles are there in the jar? ja r? 2. How will you “count” many pieces of small ob jects like grain? 3. How will you use masses and moles to count atomic particles? MATERIALS: scientific calculator, balance, beakers, marbles in a sealed jar, same type empty jars with cover, (rice, mung beans, red beans, dried corn, chick peas) items in parentheses to be brought by the students
PROCEDURE: 1. The class is going to be given a jar of marbles in the laboratory. Without opening this jar and using items that will be made available to you, make a scientific “guess” on the number of marbles in the jar. 2. Plan on how you could measure 1000, 5000 and 25000 pieces of the grain that you brought (corn, beans, etc.). You are allowed to do whatever measurements you may deem necessary on the samples of grain that you have.
QUESTIONS: 1. 2. 3. 4.
Explain how you arrived at your group “count” of the number of marbles in the jar. Write out detailed instructions on how the given measures of grain could be counted. How would you count the number n umber of rice grains in a 25 kg sack of rice? Pool data with your classmates and fill the table b elow: If more than one group worked on the same grain, take the average mass of the groups’ results.
Grain* Corn Rice Mung beans Red beans Chick peas (*any substitute)
Number of grains
Mass in g
25000 25000 25000 25000 25000 25000
Are the masses for the same number of the different grains the same? Why Wh y or why not? 5. What measurement can be used to substitute for count?
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Group No. _____
Date: _______
Names: Names: _______________ _______________________ ______________ ______ _____________________________ _____________________________
UNDERSTANDING THE MOLE
Number of Marbles in the jar: ________________
1. Explain how you arrived at your group “count” of the number of marbles in the jar.
2. Write out detailed instructions on how the given measures of grain could be counted.
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3. How would you count the number n umber of rice grains in a 25 kg sack of rice?
4. Pool data with your classmates and fill the table b elow: If more than one group worked on the same grain, take the average mass of the groups’ results.
Grain
Number of grains
Mass in g
25000 25000 25000 25000 25000 25000
Are the masses for the same number of the different grains the same? Why Wh y or why not?
5. What measurement can be used to substitute for count?
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6. The mole represents 6.022× 10 particles. Calculate the number of particles in the -7 following: (a) 0.367 mole sodium, (b) 2.50 mo le of water, (c) 9.5 × 10 mole sugar, C12H22O11
7. The mass of one mole or molar mass of a substance is its formula weight in grams. Find the molar masses of (a) Na, (b) H 2O, (c) C12H22O11
8. How many particles would be present in the following masses? (a) 350 mg Na, 1000 mg = 1 g , (b) 335 mL of water, density of water = 1.00 g/mL, (c) 500 g C12H22O11
