Academic chemistry [Type text] Name

Period Date:

The Mole

Purpose:

To discover a method of counting “things” that you are not able to see such as toms, molecules or formula units of compounds.

To use Avagadro’s number and molar mass as a bridge between mass of a sample and number of atoms, molecules, or formula units in that sample.

Introduction

Please complete the following backround questions about units for your prelab assignment

1.  When you buy eggs you usually ask for a ______. You know that one dozen of any items is______items.

2.  Paper is not packaged by the dozen. Paper is packaged by the ream. A rean of paper has 500 sheets. Why is it useful to use these units like a dozen or a ream.

3.  What determined how many items should make up a particular unit? (think about paper and eggs)

4.  If you were asked to design a new unit to count something, what would you consider when choosing how many items should be included in your new counting unit?

5.  The mole is defined as (see your notes of textbook):

The word mole is derived from the Latin “moles” which means “a mass.”

6.  What other unit is based on carbon-12 as the standard?

7.  One mole contains______items?

8.  The number associated with the mole is known as______number.

9.  If you had only one mole of carbon, how many atoms would be present?

10. How much would a mole of carbon weigh?______This is known as the molar mass of carbon and it has the same vaule as the atomic mass only it has units of grams.

Objectives

To discover a method of counting “things that you are not able to see such as toms, molecules or formula units of compounds.

To use Avagadro’s number and molar mass as a bridge between mass of a sample and number of atoms, molecules, or formula units in that sample.

Materials

Electronic balance, calculator, pencil, Carbon, silicon, sulfur, nickel, tin, iron, copper, aluminum, zinc , lead samples, small beaker, pipet, water, candle, matches, foil covered glass plate

Procedure

Please save any questions until after you have finished weighing all your samples.

Part I: Atoms of Carbon In A Pencil

Objective: to determine the number of atoms used while using your pencil during lab. Pencils have a graphite core that is commonly referred to as “lead.” However, graphite is actually an allotrope of carbon. Define allotrope:______

1.  Sharpen your pencil

2.  Mass the pencil and record the mass in the table below

3.  Complete the other sections of the lab

4.  Wipe fingerprints from the pencil and find its mass at the end of the lab

5.  Complete the calculations below showing work in the space provided

Data Part I:

Description / Value / Units
Initial mass of pencil
Mass of pencil after lab
Mass of graphite used
Moles of graphite used
Number of graphite particles used
Estimated number of C atoms in the pencil (remember the whole pencil is not graphite)

Calculations:

Molar mass of graphite (C8) = molar mass of carbon x 8=

Moles of graphite used:

Number of graphite particles used:

Part II: Molecules of Water In A Drop?

Objective: to calculate the number of water molecules in a single drop of water.

1.  Geuss the number of water molecules in a single drop of water______

2.  Obtain as small beaker or cup and find its mass

3.  Use a dropper pipet to deliver 50 drops of water to the beaker

4.  Find the mass of the beaker and 50 drops of water

5.  Complete the calculations below

Data Part II:

Description / Value / Units
Mass of empty beaker
Mass of beaker and 50 drops of water
Mass of 50 drops of water
Average mass of one drop of water
Molar mass of water
Moles of water in 1drop
Number of molecules in 1 drop

Calculations:

Molar mass of water = 2 x molar mass of H + molar mass of O =

Moles of water in 1 drop

Molecules of water in one drop:

Please show all work for the following questions (post lab)

1.  The water in the pacific ocean has a mass of 6x 1023 grams. How many moles of water are in the pacific ocean?

2.  How many molecules are in the pacific ocean?

3.  If you drink 8 (80z.) glasses of water a day, how many molecules of water do you drink? Set up as a single conversion problem.

30ml =1 fluid ounce, density of water= 1 gram/ml, 18.02 grams H2O = 1moleH2O,

1mole H2O = 6.02 x1023 molecules of H2O

Part III: Moles and Atoms in a Sample

Objective: to become familiar with mole amounts of different substances.

1.  Fill in the following data table for 5 different substances found in the lab.

Name of substance
Element symbol
Qualitative observations of the sample
Molar mass of element
Mass of the sample and the container
Mass of the container
Mass of the sample
Moles of the sample
Number of atoms

Calculations:

1.  show one sample calculation to find the number of moles in a sample starting with the mass of the sample in grams.

2.  Show one sample calculation to find the number of atoms in a sample starting with the number of moles of the sample.

Part IV: Moles and Molecules Burned In A Candle

Objective: to calculate the number of moles of C25H52 and the number of molecules used when a candle burns for a set amount of time.

*You may use your data from the introductory lab if you run out of time during the lab.*

1. weigh a glass plate. Attach the candle to the glass plate and weigh again.

2. Light the candle and allow it to burn for a set amount of time______

3. Blow out the candle and reweigh it without using any melted wax.

4. complete the data table and calculations below.

Descrition / Value / Units
Mass of the plate
Mass of candle and plate before burning
Mass of candle before burning
Mass of candle and plate after burning
Mass of candle after burning
Mass of wax used
Molar mass of wax
Moles of wax used
Molecules of wax used

Calculations:

1.  Calculate the molar mass of C25H52 (hint: 25 x molar mass of C+52 x molar mass of H)

2.  Calculate the moles of wax used.

3.  Calculate the molecules of wax used.