Making Solutions

Solutions Solute – Substance being dissolved Solvent – Substance doing the dissolving Concentration = Solute/Solvent

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

Common for making protein or DNA based solutions: 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

Make 100ml of 5mg/ml Albumin Solution Example Make 100ml of 5mg/ml Albumin Solution ________ x ________= ____________ Concentration Volume Amt. Solute Desired Desired to be Weighed 5mg/mL x 100mL = 500 mg 500 mg = 0.5 g (weigh out) QS to 100 mL

% 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 mL 10% = 10 g of SDS up to 100 mL with water

Convert % value to decimal value % 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

________ x ________= ____________ Concentration Volume Amt. Solute %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/mL 0.03 g x 100 mL = 3g CuSO4 QS to 100 mL

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

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)

Making Molar Solutions ________ x ______ x _____ = _______ Concentration Volume Molecular Amt. Solute Desired Desired Weight to be Weighed (mol/L) (L) (g/mol) (g)

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

100 mL of 2M NaCl (convert 100 mL to 0.1 L) 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 g Weigh out 11.6 8g, QS to 100 mL for 2M NaCl

Moving the Decimal Point 1000 mg = 1 g 100 mg = 0.1 g 10 mg = 0.01 g 1.25 grams is how many mg? 125.0 μL is how many mL? 1000 mL = 1 L 100 mL = 0.1 L 10 mL = 0.01 L 1 mL = 0.001 L 1000 μL = 1 mL 100 μL = 0.1 mL 10 = μL = 0.01 mL 1 μL = 0.001 mL

Frequently we use concentrated stocks 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

Make 1L of 1mg/mL protease solution from a 100 mg/mL Stock C1V1 = C2V2 Example Make 1L of 1mg/mL protease solution from a 100 mg/mL Stock C1V1 = C2V2 Convert to Like units: 1 L = 1000 mL V1 = 1 mg/mL x 1000 mL = 10mL 100 mg/mL Add 10 mL Stock to 990 mL diluent to bring to 1L