GenChem

Final Exam

Today’s Agenda:

Collect pre-lab assignment.

Locker Check-out.

Conduct written test of course material.

Review background material on paint pigments.

Discuss the problem to be addressed.

Collect data.

Analyze results.

Write and submit a report.

14th Class

GenChemLOCKER CHECK-OUTLOCKER CHECK-OUTBefore we do anything else, the preproom people will check you out of your locker. Here’s how.

You remove everything from your locker and put it on the lab bench. Make sure the inventory is complete and clean the contents to the best of your ability.

A prep person will come by and check your locker. When complete that person will give you a “drawer complete” slip.

You take the drawer complete slip to the window to get your receipt (or a bill, if there are charges). You are not done until you have your receipt or bill.

No testing will begin until everyone is finished check-out

GenChem

THE WRITTEN HALFTHE WRITTEN HALF.There is not enough room to answer the questions on the test paper. Please answer on separate sheets making sure you identify where each problem is answered. For numerical answers, put a box around the answer.

GenChemThe Practical

Problem: Adamowicz Artisans, IncAdamowicz Artisans, Inc, a

specialty art materials supplier has been contracted by Weso Weso

StudiosStudios' to make tubes of various colors of oil-based

paints.

You are assigned to come up with the pigment to be used in

one of the paints.

GenChem

The Specific Problem:

Paint PigmentPaint Pigment

More specifically, you are to identify a pigment of the correct color and then

determine how to quantitatively make the

pigment. Your report to the development team will need to contain a procedure for

making 1.0 kg batches of the pigment.

GenChem

PAINT PIGMENT

What are they?What are they?How do you make one?How do you make one?

Let′s think!

GenChem

Putting the color into paint.

What do you think makes a good pigment?

PIGMENT

A chemical compound that won’t change composition over time.

Insoluble salts of heavy metals have been popular pigments for thousands of years.

GenChemYour Pigment

For this problem you are asked to identify a metal salt of the proper color and

determine a method for quantitatively preparing that salt to use as a pigment.

GenChem

Making the Pigment

Na2S Na2CO3 K3PO4 NH4OH

Solutions of the following seven salts are available.

In your groupsIn your groups

Predict the salts that are likely to precipitate when

these solutions are mixed.

Let′s think!

Cu(NO3)2 Co(NO3)2 Fe(NO3)3

GenChemPredicting Solubility A Rule Summary

1. Salts containing Group I elements are soluble. Ammonium (NH4

+) salts are also soluble. 2. Salts containing nitrate ion (NO3

-) are generally soluble.

3. Salts containing Cl -, Br -, I - are generally soluble. 4. Most sulfate salts are soluble. 5. Most hydroxide salts are only slightly soluble. Hydroxide salts of Group I elements are soluble. Hydroxide salts of Group II elements (Mg, Ca, Sr, and Ba) are slightly soluble. Hydroxide salts of transition metals are insoluble. 6. Most sulfides of transition metals are highly insoluble. 7. Carbonates are frequently insoluble. 8. Phosphates are frequently insoluble.

GenChemMaking a Salt, QuantitativelyMaking a Salt, Quantitatively

Arsenic (III) sulfide (As2S3) is a paint pigment known as orpiment.  It is

believed to have been first used more than five thousand years ago.  It is an

insoluble salt that can be made by mixing a solution of arsenic (III) nitrate

with a solution of sodium sulfide.

Consider a painter who requires exactly 0.100 g of arsenic (III)

sulfide.  How much 0.100 M arsenic(III) nitrate and how much

0.100 M sodium sulfide will the painter need to mix together to get

exactly 0.100 g?

GenChemFollowing the logic train

0.100 g of arsenic (III) sulfide from 0.100 M arsenic(III) nitrate and 0.100 M sodium sulfide.

How much of each?

Create formula: Determine molar mass Determine moles arsenic(III) sulfide required. Determine moles arsenic (III) and sulfide

required. Determine volume of solutions required to

deliver that amount.

GenChem

Charging for hintsCharging for hints

Knowledge that can be purchased

• Formula of your salt.

• Molar mass of your salt.

• Equation for formation of your salt.

This is a timed test and there are a number of places where you could possibly get “stuck”. To prevent

catastrophic failure, should you get stuck you will be sold information to allow you to proceed. The cost will vary but

will not total more than 10% of the practical score.

GenChem

Your First Challenge

Class project: Determine which salt is your assigned color.

Available resources:

Solutions of the seven salts;

well plate.

Let′s explore!

You have only 15 minutes to figure this out.

GenChem

Your Next Challenge

Figure the volumes of solutions that need to be mixed to produce your 0.250 grams of pigment.

Let′s explore!

You have only 15 minutes to figure

this out. If you don’t have an answer in 15 minutes you’ll have

to buy one.

GenChem

1. The precipitate will filter better if you let it “age” first. A minimum of 10 minutes is recommended.

2. When drying your product using the hot plate make sure the setting is not greater than 55. Watch for charring. Move the filter paper around if it begins to char.

4. You will need a percent yield to successfully complete your report.

3. Time will be an issue for many. There are a couple of places in the procedure where you need to wait. This would be a good time to begin constructing your report.

Pointers for preparing your pigment.Pointers for preparing your pigment.

GenChem

Your personal Challenge

Design and carry out a procedure for preparing exactly 0.250 gram of your pigment.

Available resources:

solutions of the seven salts;

25-mL graduated cylinder;

100-mL beakers

funnel and filter paper.

balance

Let′s explore!

As this is a test, you are now on your own. No more group work.

You have 45 minutes.

GenChemThe Report

Report Content:

Abstract. Brief description of the report’s content.

Introduction. Background information necessary to understand the experiment.

Raw data. A copy of all measurements and observations you collected in lab.

Results. An organized presentation of the results obtained.

Calculations. Examples of the various calculations performed.

Discussion. A discussion of the results obtained, their credibility and their meaning.

You will now write your report for this

experiment.

GenChem

Your Discussion should address• The identity of your selected pigment including the

formula.

• The chemical equation for the manufacture of the pigment.

• An outline of the recommended procedure for preparing 1.0 kg batches of the pigment including your justifications for the amounts of materials required.

• Your projection of manufacturing problems that may occur based on your observations and understanding of the properties of the materials involved

Your Final Final challenge!