Making Solutions

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Solutions

• Solute – Substance being dissolved• Solvent – Substance doing the

dissolving

• Concentration = Solute/Solvent

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Concentration Typically Reported As:

• Mass/volume mg/mL • 0.5 mg/mL DNA

• % (mass/volume or volume/volume)• 1% agar

• Molarity (moles/liter) • 1M NaCl

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Mass/Volume

• Common for making protein or DNA based solutions:• mg/mL, g/L, μg/ μL

________ x ________= ____________ Concentration Volume Amt. Solute

Desired Desired to be Weighed

*May need to convert units of measurement to make math easier

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Example

• Make 100ml of 5mg/ml Albumin Solution

________ x ________= ____________ Concentration Volume Amt. Solute

Desired Desired to be Weighed

5mg/mL x 100mL = 500 mg500 mg = 0.5 g (weigh out)QS to 100 mL

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% Mass/Volume Solutions

• Often, a procedure calls for a solution made by calculating percent.• Add 10 mL of 10% SDS to your cells

• How do we make a 10% Solution of anything?

• Remember that 1% = 1 gram in 100 mL10% = 10 g of SDS up to 100 mL with water

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% Mass/Volume Cont.

• Need to factor in that the amount of solute is based on there being 100 parts of solution (100%)

• Convert % value to decimal value• Move decimal point two places to the

left• 25% = 0.25 g/mL• 50% = 0.5 g/mL• 100% = 1 g/mL

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%Mass/Volume

________ x ________= ____________ Concentration Volume Amt. Solute Desired Desired to be Weighed(as a decimal value)

• To make 100 mL of 3% CuSO4• Convert 3% to 0.03 g/mL0.03 g x 100 mL = 3g CuSO4QS to 100 mL

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Making Molar Solutions

• “Molarity” the most commonly used chemical unit of measurement• It is the number of moles of a solute

dissolved in a liter of solution• Same procedure as before, but now

must factor in the number of moles of solute

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Making Molar Solutions

• What is a “mole”?• A mole of a substance equals the gram-

formula mass…• The sum of all of the masses of all of the

elements in the formula of a substance

• If you count all of the carbon atoms in in one mole of carbon-12, there would be 6.02 x 1023 atoms, and it would weigh 12 grams (atomic weight of carbon is 12)

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Making Molar Solutions

________ x ______ x _____ = _______ Concentration Volume Molecular Amt. Solute

Desired Desired Weight to be Weighed

(mol/L) (L) (g/mol) (g)

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Don’t Panic!

• The Formula Weight (also referred to as the Molecular Weight) is on the bottle.

• Can also find it using the Periodic Table

• 1 mole of NaCl weighs 58.4 g• A molecule of NaCl weighs 58.4 amu

• Na = 23 amu• Cl = 35.4 amu

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Example

100 mL of 2M NaCl (convert 100 mL to 0.1 L)________ x ______ x _____ = _______ Concentration Volume Molecular Amt. Solute

Desired Desired Weight to be Weighed

(mol/L ) (L) (g/mol) (g)

2mol/L x 0.1 L x 58.4 g/mol = 11.68 gWeigh out 11.6 8g, QS to 100 mL for 2M NaCl

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Moving the Decimal Point

1000 mg = 1 g100 mg = 0.1 g10 mg = 0.01 g

1.25 grams is how many mg?

125.0 μL is how many mL?

1000 mL = 1 L100 mL = 0.1 L10 mL = 0.01 L1 mL = 0.001 L

1000 μL = 1 mL100 μL = 0.1 mL10 = μL = 0.01 mL1 μL = 0.001 mL

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Making Dilutions

• Frequently we use concentrated stocks• Easier to make and store

• Calculating how much stock solution to use to make a desired dilution:

C1V1 = C2V2

C1 Concentration of the Stock Solution

V1 Volume to use of Stock (Solve for this)

C2 Desired Concentration of diluted Stock

V2 Desired Volume of the diluted Stock

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Example

• Make 1L of 1mg/mL protease solution from a 100 mg/mL Stock

C1V1 = C2V2

Convert to Like units: 1 L = 1000 mLV1 = 1 mg/mL x 1000 mL = 10mL

100 mg/mL

Add 10 mL Stock to 990 mL diluent to bring to 1L