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Transcript of Take Home · Web viewHow many grams of potassium sulfate (K2SO4) are there in 25.3 moles?...

Take Home Lab

Name ______________

Period _______

Name_________________

Period________

Unit 3 Packet: The Mole

Name

WPHS Chemistry

Unit 3

The Mole

Chemistry: Unit 3 Outline: The Mole

Assignment

Can only be done in class?

Podcast 3.1 - The Mole

Worksheet 3.1

Lab: Pennies

Yes

Podcast 3.2 Molar Mass

Worksheet 3.2

Podcast 3.3 Mole Conversion (One Step)

Worksheet 3.3

Podcast 3.4 Mole Conversion (Two Steps)

Worksheet 3.4

Lab: Mole Lab

Yes

Mole Video (Dr. Don)

Demo: Measure out 1 mole of NaCl, H2O, NaHCO3 and show to your teacher

Yes

Podcast 3.5 % - Composition

Worksheet 3.5

Podcast 3.6 - Empirical Formula

Worksheet 3.6

Podcast 3.7 Molecular Formula

Worksheet 3.7

Lab: Magnesium and Oxygen Empirical Formula

Yes

Review

Unit 3 Exam (You must score 75/100 to move to the next unit)

Yes

Unit 3 Vocabulary

Mole

Avogadros Number

Representative Particle

Atomic Mass/Gram Atomic Mass)

Molecular Mass/Gram Molar Mass

Gram Formula Mass

Molar Mass

STP

Molar Volume

Percent Composition

Empirical Formula

Molecular Formula

PENNY COUNTING BY WEIGHING

PURPOSE: To make a model of counting by weighing.

MATERIALS: A handful of pennies, a balance

PROCEDURE:

1. Determine the average mass of a penny by weighing 25 pennies and dividing the total mass by 25.

2. Repeat step 1 two more times with different pennies, and take the average of your three results.

3. Weigh about three-fourths of you total number of pennies.

4. Calculate how many pennies you weighed.

5. Count the number of pennies in your sample and compare that to the number you calculated in steps 3 & 4.

6. Repeat steps 3,4 and 5 with a different sample size.

DATA TABLE:

QUESTIONS:

1. Did the number of pennies you counted in the sample (step five) equal the number you calculated by weighing (step four)? If there was not agreement, propose an explanation.

2. Explain how you would use the balance to count out 185 pennies.

3. What is the advantage of using a larger sample size in step 1? What is a disadvantage?

4. How are the pennies like atoms in this experiment?

Mole Lab: Making a precipitate of BaSO4

Background: The unit of measure for the amount of a substance is the mole. A mole is 6.02 x 1023 particles (such as atoms or molecules). The mass of one more of any substance is found using the periodic table (calculate molar mass).

Purpose: The purpose of this lab is to measure chemical quantities.

Materials: small test tubes, balance, weigh boat, CaCl2, Na2SO4, H2O, centrifuge, graduated cylinder

Calculations:

Convert moles of calcium chloride to grams

Convert moles of sodium sulfate to grams

Procedure:

1. Weigh 0.0025 mole of calcium chloride and place in one test tube

2. Weigh 0.0035 mole of sodium sulfate and place in another test tube

3. Add water to the test tube such that it is 1/3 full.

4. Agitate (shake or tap) each mix until the chemical inside it dissolves. You may want to have your teacher show you an easy way to do this.

5. After both substances have completely dissolved pour the sodium sulfate solution into the barium chloride solution.

6. Place the test tube in the centrifuge, making sure that another groups (Or another test tube with roughly equal weight) test tube is directly across from your test tube and allow the centrifuge to run for 1 minute SAFETY: Take care with the centrifuge: It spins at a very high speedkeep fingers away from the spinning centrifugeit can take your finger OFF!!

7. Bring your test tube to your teacher to check the amount of precipitate and sign your groups papers

Questions:

1. What is the evidence that a chemical reaction has occurred?

2. When you mixed the two solutions, you created BaSO4. What is the name of this chemical?

MAGNESIUM OXIDE PRODUCTION

Objectives: In this investigation, you will

prepare magnesium oxide,

calculate the percent composition of your product, and

determine the products empirical and molecular formulas.

Equipment:

crucible and cover

tongs

Bunsen burner

clay triangle

ring stand

iron ring

wash bottle

glass stirring rod

15 cm Mg ribbon

analytic balance

distilled water

GOGGLES

Procedure:

1. Wash and dry your hands (moisture on your hands will react with the magnesium ribbon).

2. Record the mass of a clean, dry crucible and cover.

3. Obtain a piece of magnesium ribbon approximately 15 cm long from your instructor and scrape both sides of the magnesium with the scissor blade to remove corrosion (when the corrosion is removed the Mg will appear shiny). Coil the Mg loosely around a pencil. Remove the pencil, place the magnesium in the crucible and record the mass of the magnesium, crucible and lid.

4. Place the crucible, cover and magnesium on a clay triangle as shown in the figure.

5. Adjust the crucible and cover on the clay triangle so that the lid is ajar. This position will allow a steady flow of air into the crucible. Heat the crucible gently for 3 minutes then strongly for 5 minutes. CAUTION: Do not look directly at the burning magnesium. Allow the crucible to cool for 5 minutes. CAUTION 2: Do not add cold water to a hot crucible: It will crack!!

ANALYSIS: Show all measurements and calculated numbers in the spaces provided in the data table. (Show units and substance symbol or formula for each measurement taken or number calculated.)

Measurement

mass of crucible, cover, and Mg before heating

mass of empty crucible and cover

mass of magnesium

mass of crucible, cover and residue after heating

mass of residue (magnesium oxide produced)

Mass of oxygen

moles of oxygen in the magnesium oxide residue

moles of magnesium in the magnesium oxide residue

Calculations:

Calculate the percent composition of magnesium oxide (write the formula, balancing the charges of the Mg ion and the O ion, then find the percent composition by mass).

From your measured value of the mass of residue in your data table, calculate the moles of magnesium and of oxygen in your sample of residue.

Using the moles calculated above; calculate the empirical formula for your sample of magnesium oxide.

Using the empirical formula found above, what is its molecular formula if the molar mass is 40.3 g/mol?

Questions

1. Does the magnesium in your crucible gain or lose mass? Explain.

2. How would your final ratio change if not all of the magnesium had reacted?

3. How would your final ratio change if there were still some water in the crucible after you stopped heating it?

4. Does your calculated formula for magnesium match the predicted formula (questions #6)?

The World of Chemistry: Episode 11 - The Mole: Video can we watched at http://learner.org Search for the series World of Chemistry and look for episode 11.

1. Why is it important to use the correct amount of materials in a chemical reaction?

2. What names are given to the materials at the beginning and end of a chemical reaction?

3. Atoms and molecules are extremely small. How do chemists "count" them? Can you think of an everyday application of this?

4. a. What did early chemists discover about reactions involving the combination of gases?

b. How did Avogadro explain this?

5. How may a chemical equation such as H2 + Cl2 ( 2 HCl be interpreted?

6. What is true about the mass of a compound?

7. What is the numerical value for Avogadro's Number?

8. When the I V solutions were prepared, quality control was involved. What is quality control?

9. Why did using twice as much magnesium not produce twice as much hydrogen in the demonstration?

10. What ratio of starting materials was found to produce the best epoxy resin?

WS 3.1 The Mole

1. Describe/relate the size of the mole to an everyday object.

2. What is Avogadros Number?

3. How many marbles are in a mole of marbles?

4. How many mosquitoes are in a mole of mosquitoes?

WS 3.2 Molar Mass

Find the molar mass of the following compounds: Show work and include units

1. CO2

2. Fe2O3

3. AgCl

4. Ca3(PO4)2

5. W3(PO3)5

6. Fe(C2H3O2)2

7. Calcium Carbonate

8. Lead IV Sulfate

9. Lead IV Sulfite

10. Lead IV Sulfide

11. Lead II sulfate

12. Lead II Sulfite

13. Lead II Sulfide

14. Copper I Sulfide

15. Copper II Sulfite

WS 3.3: Mole Conversions (one step)

Directions: Answer the following questions. Set-up all problems using the factor-label method of dimensional analysis and show all your work and units.

1. How many atoms are in 1.5 moles of neon?

2. How many moles of SF6 are there in 4,595,000,000,000,000,000 molecules of SF6?

3. Calculate the number of moles in 5.45x1025 atoms of Zn

1. What is the mass of 7.50 moles of sulfur dioxide (SO2)?

2. How many moles are there in 250.0 grams of sodium phosphate (Na3PO4)?

3. How many grams of potassi