Week 12

10/30-11/3

Agenda 10/30

• Finish Lab 3e
• Clean up - cuvettes, CuSO₄(waste & measuring), conicals
• Lab 3e Data Analysis - error analysis only

HW - Finish Lab 3e

Agenda 10/31

• Lab 3f Write up
• Title
• Purpose
• Materials
• Safety
• Procedure - do not include Part I; Part IV modifications on slides
• Data Tables & Calculations w/ Diagrams (3.14 & 3.15)

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Part IV

• Add 1 mL of the gelatin solution to be tested into a 2-mL microtube. Save all unused samples.
• Add the 10% NaOH solution and 5% CuSO₄ in a 2:1 ratio shown in Table 3.15. First, add the NaOH to the sample in the microtube, then add the CuSO₄.
• After 1 minute, record the color changes…

Continue the instructions as per the lab manual.

Agenda 11/3

• Check calcs with me first! - Lab 3f Parts II, III & IV
• Label glass tubes VERY well - boiling water may remove labels (top of the tube?)
• Parafilm will be used to cover your tubes if necessary (for storage)
• Make sure YOUR TUBES get put in the storage rack (if they need to be stored)
• Lab 3f Data Analysis/Conclusion

Lab 3f Data Analysis/Conclusion

• Describe the results of the Biuret testing of the gelatin solutions of decreasing concentration.
• Do the colors indicate the expected difference in concentration? How so or not?
• Describe any errors in technique that could result in misleading data.
• What might be done to decrease the chances of erroneous data or interpretation?
• Explain how the results of these Biuret protein tests could be applied to testing other solutions of unknown concentration.

Agenda 10/27

• Molarity Notes
• Making Solutions Review Sheet #2 (p. 54 lab manual)
• Section Review Questions 3.2-3.6
• Update NB for collection

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Turn in Notebooks

Electrolytes and Non-Electrolytes

Electrolyte: A substance that dissolves in water to give a solution that conducts electric current. (Ex. NaCl in water)

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Non-electrolyte: A substance that dissolves in water to give a solution that does not conduct electric current. (Ex. Sucrose in water)

Molar Mass

The sum of the masses of all the atoms in the element, formula or molecular substance.

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You will need your periodic table of elements to obtain the molar masses of each of the elements.

Molar Mass

• Calculating Molar Mass
• CH₄ – contains:
• 1 C Atom & 4 H atoms
• Usually written g/mol
• g = grams
• mol = mole

Molar Mass

Mass of 1 mol of C = 1 x 12.01 g = 12.01 g

Mass of 4 mol of H = 4 x 1.008 g = 4.032 g

Mass of 1 mol of CH4 = 16.04 g

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Molar Mass of CH₄ = 16.04 g/mol

You Try!

Calculate the Molar Mass of ...

• Calcium Chloride
• Sodium Hydroxide
• Copper Sulfate Pentahydrate

Answers

Calcium Chloride = CaCl₂ = 110.98 g/mol

Sodium Hydroxide = NaOH = 40.00 g/mol

Copper Sulfate Pentahydrate = CuSO₄ · 5H₂O = 249.68 g/mol

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The Mole

• SI unit for amount of substance
• A mole (mol) is the amount of a substance that contains as many particles as there are atoms in 12 g of Carbon-12.
• The mole is the counting unit, just like the term dozen is used.
• We will see how the mole relates to masses of atoms and compounds.

Calculations

• Use the factor label method
• Start with the end in mind
• List your given
• Use the appropriate conversion factor
• Check your units

Mass to Moles

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Calculate the number of moles in 5.00 grams CO₂

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Mass to Moles

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Calculate the number of moles in 5.00 grams CO₂

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Concentration of Solutions

The concentration of a solution is a measure of the amount of solute that is dissolved in a given quantity of solvent.

• A dilute solution is one that contains a small amount of solute.
• A concentrated solution contains a large amount of solute.

Molarity

Molarity (M) is the number of moles of solute dissolved in one liter of solution.

To calculate the molarity of a solution, divide the moles of solute by the volume of the solution.

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*Molarity is a capital “M” and the units are mol/L.

Conversion Factors - Recall!

Recall the following conversion factors:

1000 mL = 1 liter (L)

1000 mg = 1 gram (g)

Calculating Molarity

Steps in Calculating Molarity Problems:

• Begin with the end in mind (Molarity is mol/L)
• List your given.
• Convert to moles of solute if not in the given (use molar mass to do this)

Remember you want moles on top

• Divide by liter of solution (convert to liters using conversion if liters is not given)

Remember you want liters (L) on the bottom

Calculating Molarity - Practice

Intravenous (IV) saline solutions are often administered to patients in the hospital. One saline solution contains 0.90 g NaCl in exactly 100 mL of solution. What is the molarity of the solution?

Applicable Practice

I want 500 mL of a 5M solution of CuSO₄•5H₂O. How many grams of CuSO₄•5H₂O do I need?