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SolutionsSolutions

Why does a raw egg swell or shrink when Why does a raw egg swell or shrink when placed in different solutions?placed in different solutions?

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Some DefinitionsSome DefinitionsA solution is a A solution is a

HOMOGENEOUSHOMOGENEOUS mixture of 2 or more mixture of 2 or more substances in a substances in a single phase. single phase.

One constituent is One constituent is usually regarded as usually regarded as the the SOLVENTSOLVENT and and the others as the others as SOLUTESSOLUTES..

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Parts of a Solution• SOLUTE – the part

of a solution that is being dissolved (usually the lesser amount)

• SOLVENT – the part of a solution that dissolves the solute (usually the greater amount)

• Solute + Solvent = Solution

Solute Solvent Example

solid solid Alloys (brass, steel)

solid liquid Salt water

gas solid Air bubbles in ice cubes

liquid liquid “suicides” (mixed drinks)

gas liquid Soft drinks

gas gas Air

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IONIC COMPOUNDSIONIC COMPOUNDSDissolve in water! Dissolve in water!

Create Aqueous SolutionsCreate Aqueous Solutions

KMnOKMnO44 in water in water KK++(aq) + MnO(aq) + MnO44--(aq)(aq)

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Concentration of SoluteConcentration of SoluteConcentration of SoluteConcentration of Solute

The amount of solute in a solution The amount of solute in a solution is given by its is given by its concentrationconcentration.

Molarity (M) = moles soluteliters of solution

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Think of O.J!

• Do you like Concentrated Orange Juice?

• What does that mean?

• What if we could describe the amount of Orange Juice in a solution.

• That’s why we have Molarity!!!

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To make a 1 M To make a 1 M solution of solution of Copper (II) Copper (II)

SulfateSulfate

Add 1 Mole of Add 1 Mole of Copper SulfateCopper Sulfate

Add Enough Add Enough water so that the water so that the SOLUTION has a SOLUTION has a

volume of 1 Lvolume of 1 L

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PROBLEM: Dissolve 5.00 g of PROBLEM: Dissolve 5.00 g of NiClNiCl22•6 H•6 H22O in enough water to O in enough water to make 250 mL of solution. make 250 mL of solution. Calculate the Molarity.Calculate the Molarity.

PROBLEM: Dissolve 5.00 g of PROBLEM: Dissolve 5.00 g of NiClNiCl22•6 H•6 H22O in enough water to O in enough water to make 250 mL of solution. make 250 mL of solution. Calculate the Molarity.Calculate the Molarity.

Step 1: Step 1: Calculate moles Calculate moles of NiClof NiCl22•6H•6H22OO

5.00 g • 1 mol

237.7 g = 0.0210 mol

0.0210 mol0.250 L

= 0.0841 M

Step 2: Step 2: Calculate MolarityCalculate Molarity

[NiClNiCl22•6 H•6 H22OO ] = 0.0841 M

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Step 1: Step 1: Change mL to L.Change mL to L.

250 mL * 1L/1000mL = 0.250 L250 mL * 1L/1000mL = 0.250 L

Step 2: Step 2: Calculate.Calculate.

Moles = (0.0500 mol/L) (0.250 L) = 0.0125 molesMoles = (0.0500 mol/L) (0.250 L) = 0.0125 moles

Step 3: Step 3: Convert moles to grams.Convert moles to grams.

(0.0125 mol)(90.00 g/mol) = (0.0125 mol)(90.00 g/mol) = 1.13 g1.13 g

USING MOLARITYUSING MOLARITYUSING MOLARITYUSING MOLARITY

moles = M•Vmoles = M•V

What mass of oxalic acid, What mass of oxalic acid, HH22CC22OO44, is, is

required to make 250. mL of a 0.0500 Mrequired to make 250. mL of a 0.0500 Msolution?solution?

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Learning Check

How many grams of NaOH are required to prepare 400. mL of 3.0 M NaOH solution?

1) 12 g

2) 48 g

3) 300 g

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Solution

M = moles of solute Liters of solution

M * V = moles3.0 mol/L * 0.400 L = 1.2 mol NaOH

1.2 mole NaOH x 40.0 g NaOH 1 mole NaOH

= 48 g NaOH

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Preparing SolutionsPreparing SolutionsPreparing SolutionsPreparing Solutions

• Weigh out a solid Weigh out a solid solute and dissolve in a solute and dissolve in a given quantity of given quantity of solvent.solvent.

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Mixing SolutionsMixing SolutionsMixing SolutionsMixing Solutions

How would you make 500.mL of a 2.50M How would you make 500.mL of a 2.50M NaOH solution?NaOH solution?

Step 1: Step 1: Convert volume mL to L.Convert volume mL to L.

500.mL * 1L/1000mL = .500L500.mL * 1L/1000mL = .500L

Step 2: Step 2: Calculate number of moles NaOH Calculate number of moles NaOH needed.needed.

moles = M * litersmoles = M * liters

moles = 2.50M * .500L = 1.25 moles NaOHmoles = 2.50M * .500L = 1.25 moles NaOH

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How can you “Dilute Solutions”

• MV=MV

How would you make 100 mL of a .1 M NaOH solution from a 1 M stock solution?

(.1L)(.1M/L) =1M X

1M

.01 L or 10 mL and add 90 mL of water

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Your tasks…

• Make 20 mL of a .100M Sucrose solution

• Create 30 mL of a .2 M solution from a Stock solution of 2 Molar Iodine Solution

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• What is a volumetric flask?

• Using the stock solution 2.30M NiCl2 Solution make another, more dilute, solution of known concentration.

• From the new dilute solution make another even more dilute solution of known concentration.

• From the second new dilute solution make a third dilute solution of known concentration that will be the most dilute.

DilutionsDilutionsDilutionsDilutions