Concentration Slides

Mixtures and Solutions Mixtures – two or more components physically intermixed but not chemically bonded –Solutions – homogeneous mixtures of components Solvent – substance present in greatest amount Solute – substance(s) present in smaller amounts –Colloids - heterogeneous mixtures whose solutes do not settle out –Suspensions - heterogeneous mixtures with visible solutes that settle out

Concept of Concentration Concentration refers to the amount of a substance in a given volume A critical concept to master

Units of Concentration Percent – parts per hundred PPM – parts per million PPB – parts per billion Molarity – moles per liter Molality – moles particles per kg solvent Mass/volume –g/ml (gram per milliliter) –mg/ml (milligram per milliliter ) –  g/ml (microgram per milliliter) Mass/Mass –mg/kg body mass –  g/kg body mass

Molecular Weight, Moles & Molarity Molecular weight –The mass of a mole of atoms or molecules –Has units of g/mole –= atomic weight of an atom in grams 1 mole of C = 12 g OR C is 12g/mole –Molecule’s molecular weight = sum of the atomic weights of its atoms 1 mole of H 2 O = 1g + 1g + 16g = 18 g MW of H 2 O = 18g/mole

Molecular Weight, Moles & Molarity What’s a mole?? –The number of molecules in the gram molecular weight of that molecule –Always 6.02 x –This magical number is Avogadro’s Number –MW of C = 12 there are 12g C/mole C there are 6.02 x C atoms in 12g of C –MW of H 2 O = 18 there are 18g H 2 O/mole H 2 O there are 6.02 x H 2 O molecules in 18g of H 2 O

Molarity – The Standard of Chemical Concentration Terms Molarity = moles of solute per liter (L) of solvent Abbreviated with M –A 5M NaCl solution contains 5 moles of NaCl molecules per liter of solution So 1 L of a 5 M NaCl solution contains 5 moles or 3.01 x molecules of NaCl

Calculating Molarity Chemical formula for glucose is C 6 H 12 O 6 MW = 180 g/mole What is concentration of glucose in a can of coke? –42g of glucose/355ml H 2 O –How many moles of glucose? – 42g / 180g/mole = moles –How many liters of coke? – 355 ml / 1000ml/L = L –How many moles/liter? – moles/0.355 L = M

Examples using Molarity Ion concentrations in cells & body fluids –[Na] = 0.15M outside cells & 0.015M inside cells –[K] = 0.005M outside cells & 0.15M inside cells Molar is often converted to millimolar (mM) –M = moles/L –mM = millimoles/L –0.15M = 150mM –Simply multiply M by 1000 to convert M to mM

Mass/Volume & Percent Concentration Terms Many molecules in the body are measured in mass/volume Normal glucose = 100mg/dL –or 100mg/100ml –or 1mg/ml or 1g/L –or 0.001g/ml –or 0.1g/100ml Cholesterol should be below 200mg/dL –or 0.2g/dL –or 0.2g/100ml Many substances are described in percentages –Percentage is g/100g or g/100ml –Blood [glucose] would = 0.1% –Blood [cholesterol] would = 0.2%