Solution Concentration Review20

8/11/2019 Solution Concentration Review20

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Solution Concentration

Which Formula

Should I Use?


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Solution Concentrations

Used in Lab

Mass/Volume: g/L or mg/ml

Percent: %

Molar: M, mM or M


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Mass/Volume Concentration

Expressed as a specific mass

per specific volume

Mass may be g, mg, g, etc

Volume may be to be L, ml, l, etc

xamples X g OR X mg OR Xg OR Xg

L ml l ml


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Mass/Volume Concentration

Tips

Formula weight does not matter!

Set up as a fraction Simplify the fraction until the denominator is

equal to 1

Used to re-hydrate packaged vials and makemedia


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Percent Solutions

X% (w/v) solution = X grams solute

100 ml solution

OR

X% (v/v) solution = X ml solute

100 ml solution


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Percent Solutions Tips

Formula weight does not matter!

Solidsolute indicates w/v Liquidsolute indicates v/v

Gel concentrations expressed this way

Look for %


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Molar Solutions

g = M FW L

g =grams of solute to be weighed out

M = molarity of the desired solution

FW = formula weight of the solute

L= volume of desired solutionexpressed in liters


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Molar Solutions Tips

Formula weight does matter

Solute is dry

Volume must be expressed in liters Usually solving for g

Add any water(s) of hydration to the FW of the

solute

Look for M or mM or M


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Sometimes you need to dilute a stock

solution in order to make a working

solution

Diluting Solutions


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Diluting Concentrated

Solutions

C1V1= C2V2

C1= concentration of stock solution

V1= volume of stock solution needed

C2= desired concentration of working solution

V2= desired volume of working solution


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Diluting Solutions Tips

Stock buffers diluted this way

Solute is liquid Volume usually expressed in ml

Usually solving for V1

Look for X


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Now that you know how to use the formulas,

lets practice knowing which formula to use.

The following slides will give you practice

problems for making solutions in the lab. Read

each problem, select which formula you needto apply, and see if you can solve the problem.

Practice!


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Directions

Each practice problem will give you four

formula choices. Choose the formula that

applies to the problem. Then solve the

problem yourself.

On each CORRECT!! slide, click to see the

problem set-up, then click again for the

solution so you can check your answer.

Then click the blue button to go to the next

problem.


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Practice #1

You need to make 1L

of LB/Amp media.

The concentration ofAmp in the media

should be 0.1 mg/ml.

How much Amp

powder do you needto weight out?

g = M FW L

C1V1= C2V2

X grams solute

100 ml solution

mass/volume

choose formula:


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Practice #2

We purchase PBS

as a 20X stock

solution. How wouldyou make 150 ml of

1X PBS?

g = M FW L

C1V1 = C2V2

X grams solute

100 ml solution

mass/volume

choose formula:


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Practice #3

Binding Buffer is 4M

Ammonium Sulfate

[(NH4)2SO4].How would you make

300 ml of

this solution?

g = M FW L

C1V

1= C

2V

2

X grams solute

100 ml solution

mass/volume

choose formula:


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Practice #4

A 30 mg vial ofAmpicillin isrehydrated with

3 ml of sterile distilledwater. What is theconcentration of

ampicillin in thissolution?

g = M FW L

C1V

1= C

2V

2

X grams solute

100 ml solution

mass/volume

choose formula:


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Practice #5

Methylene Blue is

used to stain DNA.

How would you make250 ml of a 0.5%

solution of Methylene

Blue using powdered

Methylene Blue?

g = M FW L

C1V

1= C

2V

2

X grams solute

100 ml solution

mass/volume

choose formula:


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Practice #6

Your protocol calls

for a 30 ml, 0.8%

DNA gel. How muchagarose powder do

you need?

g = M FW L

C1V

1= C

2V

2

X grams solute

100 ml solution

mass/volume

choose formula:


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Practice #7

You need 10 mM

EDTA solution to

dilute your DNA.How would you make

50 ml of

10 mM EDTA?

g = M FW L

C1V1= C2V2

X grams solute

100 ml solution

mass/volume

choose formula:


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Practice #8

We have 50X TAE.

You need 1X TAE to

run your gel. Howwould you make 400

ml of 1X TAE?

g = M FW L

C1V1= C2V2

X grams solute

100 ml solution

mass/volume

choose formula:


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Practice #9

How would you

prepare 250ml of a

40mM solution ofMagnesium Chloride

[MgCl26H2O]?

g = M FW L

C1V1= C2V2

X grams solute

100 ml solution

mass/volume

choose formula:


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Practice #10

We have 2M glucose

solution. How would

you make 100 ml of2mM glucose

solution?

g = M FW L

C1V1= C2V2

X grams solute

100 ml solution

mass/volume

choose formula:


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CONGRATULATIONS!

By carefully reading

the problems and

picking out theunknown, you were

able apply the correct

formula and do the

math!

Solution Concentration Review20

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