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Mole Laboratory

Materials & Apparatus:

Scale

Graduated cylinder(s)

Paper or plastic cups (8 oz or 16 oz)

New container of small candy (jelly beans, Skittles, M&M’s,or raisins)

New container of cereal (any cereal that is a single shape andrelatively small such as Cheerios, Kix, or Captain Crunch)

Water

Sodium Chloride (table salt)

Sucrose (white sugar)

Background:

Chemical reactions and formulas are based on the number orproportion of atoms and molecules. This means we must be able tocount atoms and molecules. Since it is not practical forchemists to count such small particles, we use a technique called“counting by mass”. We must determine the mass of large numbers ofmolecules in the laboratory because of the limitations of ourequipment. How many particles are in a certain mass? AmadeoAvogadro invented a way to determine this. He found that if youmeasure 12.00000 g of the isotope carbon-12, you will have 6.022 x1023 atoms of carbon-12. Likewise, if you measure 6.022 x1023 atoms of a particular element on the periodic table, youwould have a mass in grams equaling the atomic mass of thatelement.

This number has been called Avogadro’s number. It is equal toone mole. A mole can be used as a dozen. One dozen is 12 items andone mole is 6.022 x 1023items. Knowing this, we can“count” atoms, and their corresponding molecules, by merelymeasuring their mass. We can then use the atomic mass as aconversion factor (g/mole) to convert the number of atoms into thenumber of moles. By adding up all the atomic mass units of theatoms that comprise a molecule, we can obtain the molecular weightin g/mole. In fact, we can write formulas and chemical equations interms of moles instead of atoms and molecules. Thus, we havebrought the invisible world of extremely small particles into thelaboratory where we can use this counting by mass to study chemicalformulas and reactions.

Procedure:

Part 1 – Counting by Mass

Look at the mass indicated on the front of your package ofcandy and record the value for Assignment Question 3.

Determine the mass of an empty plastic or paper cup.Record the value in Data Table 1.

Fill the cup with your chosen candy.

Estimate the number of pieces of candy in the cup (DO NOT COUNTYET!). Record your estimate.

Determine the mass of the full cup and record the value.

Determine the mass of 5 pieces of candy individually andcalculate the average mass of a single piece of candy.

Determine the net mass of all the pieces of candy and divide itby the average of the five individual pieces of candy. Record thisestimate of the number of pieces of candy.

Note: There should be no fractions of candy. The estimate basedon your calculations should be a whole number.

Count the pieces of candy and record the exact numberin Data Table 1.

Part 2 – Counting by Mass

Look at the mass indicated on the front of your box ofcereal and record the value for Assignment Question 5.

Determine the mass of an empty plastic or paper cup. Record thevalue in Data Table 2.

Fill the cup with your chosen cereal.

Estimate the number of pieces of cereal in the cup (DO NOT COUNTYET!). Record your estimate.

Determine the mass of the full cup and record the value.

Determine the mass of 10 pieces of cereal individually andcalculate the average mass of a single piece of cereal.

Determine the net mass of all the pieces of cereal and divide itby the average of the ten individual pieces of cereal. Record thisestimate of the number of pieces of cereal.

Note: There should be no fractions of cereal. The estimate basedon your calculations should be a whole number.

Count the pieces of cereal and record the exact numberin Data Table 2.

Part 3 – How Much is a Mole?

For each of the 3 substances (water, sodium chloride, andsucrose), calculate the mass of one mole of thesubstance. Show all your work in Data Table 3.Measure out 1mole into an appropriately sized cup.

Note: Don’t forget to take into account the mass of the cup whenyou measure.

Also, you may need to use multiple cups or pour it into anothercontainer as your scale has a maximum capacity of 550 g.

Submit a digital picture of a mole of each of thesubstances with your lab report. Each substanceshould be labeled in the picture.

For water, once you have weighed out 1 mole of water, pour itinto your 25 mL graduated cylinder and measure the volume that 1mole of water occupies.

Data Table 1

Type of candy used
Estimated # of pieces of candy
Net wt. on front of candy package (g)
Mass of empty cup (g)
Mass of full cup (g)
Net mass of candy (g)
Mass of 5 pieces of candy (g)
Average mass of 1 piece of candy (g)
Calculated # of pieces of candy in cup
Actual count

Data Table 2

Type of cereal used
Estimated # of pieces of cereal
Net wt. on front of cereal package (g)
Mass of empty cup (g)
Mass of full cup (g)
Net mass of cereal (g)
Mass of 10 pieces of cereal (g)
Average mass of 1 piece of cereal (g)
Calculated # of pieces of cereal
Actual count

Data Table 3

Molar mass of water (g/mole)
Molar mass of sodium chloride, NaCl (g/mole)
Molar mass of sucrose, C12H22O11 (g/mole)
Grams of water in picture
# of mL for 1 mole of water
Grams of NaCl in picture
Grams of sucrose in picture

Assignment Questions (all work must be shown for allcalculations):

Using the results of your lab, complete all the questionsbelow.

Complete all Data Tables located in the Procedure. Make sure toinclude all your work for all the calculations performed.

In part 1, which method (estimating by looks or counting bymass) gave you the most accurate estimate of the number ofpieces of candy. How do you think the size and shape ofyour candy may have contributed to your most accurate estimationmethod? Explain.

What was the net weight of your package of candy?Using the same average mass determined in the lab, how many totalpieces of candy were in the fullpackage?

In part 2, which method (estimating by looks or counting bymass) gave you the most accurate estimate of the number ofpieces of cereal. How do you think the size and shape of yourcereal may have contributed to your most accurate estimationmethod? Explain.

What was the net weight of your box (or package) ofcereal? Using the same average mass determined in the lab, how manytotal pieces of cereal were in thefull box?

How many potassium atoms are in 2.112 g of potassium manganate,K2MnO4?

(Remember: There are 2 atoms of potassium in every molecule ofpotassium manganate)

If a diamond is made out of pure carbon and has a density of3.52 g/cm3, how large would a mole of carbon atoms (in diamondform) be in cm3? Compare this volume to thevolume that 1 mole of water occupies recorded inData Table 3.

Answer rating: 100% (QA)

In part 1 which method estimating by looks or counting by mass gave you the most accurate estimate of the number of pieces of candy How do you think t... View the full answer