Solution Concentrations Acids and Bases

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Solution Concentrations / Acids and Bases
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Solution Concentrations

• Descriptive
• 1. Dilutefew solute particles
• 2. Concentratedmany solute in given amount of
  solvent
• 3. Saturatedmaximum solute in given amount of
  solvent
• 4. Unsaturatedless than maximum solute/solvent
  ratio
• 5. Supersaturated-unstable special condition
  with solute/solvent over normal maximum

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Solution Concentrations

• Quantitative
• Molaritymoles solute per liter of solution
• a. Find moles solute
• b. Find liters solution
• c. Solve for molarity

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Molarity Calculations
M mol g 1 mol mol mols MM
grams L MM
1 mol L mol mol M x L
M Dilution Equation M1V1 M2V2
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Example 10-1

• How many grams of NaCl are needed to make 1.00 L
  of a 0.100 M solution?
• How many mL of 2 M HCl are needed to get 1 mol of
  HCl?

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Concentrations

• Weight / weight(grams solute / grams solution) x
  100
• Volume / volume (if solute is liquid)(mL solute
  / 100 mL solution) x 100
• Weight / volume(grams solute / 100 mL solution)
  x 100
• Milligrams -- (milligrams solute / 100 mL
  solution) x 100-- used for very small
  concentrationstrace minerals in blood

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Example 10-2

• How many grams of NaHCO3 need to be added to 150
  mL water to make a 0.4 w/v solution?
• How many mg of sodium phosphate need to be added
  to 20 mL of solution to make it 9.0 mg?

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Very Dilute Concentrations

• Parts per millionmg solute / 1000 mL solution
  like 10 cents to 100,000
• Parts per billion -- ?g solute / 1000 mL
  solution--Used for finding levels of contaminants
  in air or water, harmful chemicals

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Example 10-3

• If a sample of evaporated milk has 3.2 ppm of
  lead, how many grams of lead are in 470 mL of
  this milk?
• If a child has a blood concentration of 55 mg Pb/
  100 mL, what is this in ppm and ppb?

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NormalityEquivalents

• Equivalent 1 mole of charge ( or -)
• 1 eq. of Na 1mol
• But 1 eq. of Ca2 ½ mole
• This is due to calcium having 2 charges
• Normality- equivalents per liter
• Ions in blood measured in milliequivalents per
  liter of blood

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Example 10-4

• How many milliequivalents of calcium ions are in
  100 mL of a 0.1 w/v Ca2 solution?

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Homework 10a

• CYU p. 230 all
• CYU p. 232 all
• CYU p. 234
• CYU p. 236 all

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Dilution

• Reducing concentration by adding solvent
• a. Done to conserve spaceconcentrated stock is
  stored, dilutions made as needed.
• b. M1V1 M2V2 in molarity, but any
  concentration units may be used in place
• of M

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Example 10-5

• How many mL of 6.0 M HCl is needed to make
• 100 mL of 1.5 M HCl?
• What is the final concentration of a 15 dilution
  of 100 mL of 15 NaCl?

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Colligative Properties

• Depend only upon how many particles are present,
  not on what they are
• Osmotic Pressure
• Vapor Pressure Lowering
• Freezing Point Depression
• Boiling Point Elevation

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Osmotic Pressure

• Pressure to keep solvent from flowing across a
  semi-permeable membrane into a solution
• 1. Water naturally flows into solutions
• 2. Can be reversed to make pure water from
  solutions such as seawater or (Saudi)
• 3. Natural exampletrees lose water from
  leaves, become more concentrated, water flows up
  from roots by osmotic pressure

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Osmotic Pressure

• Blood solutions have to account for this
• a. Isotonicsame osmotic pressure (as blood or
  tears)
• b. Hypotonicless pressurecauses water to go
  into cells, swelling them to rupture-- hemolysis
• c. Hypertonicmore pressure, water goes out of
  cells, leaving them dehydrated and shriveled--
  crenation
• d. Intravenous solutions must always be isotonic
  with blood
• e. Edema (swelling of body parts) happens if
  blood becomes less concentrated and water remains
  in tissues. Caused my malnutrition or kidney
  failure
• f. Dialysis for kidney failure takes advantage of
  osmotic pressure to clean the blood of patients

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Vapor Pressure Related

• 1. Vapor pressure is lowered because solute
  particles compete for space at the surface thus
  making vapor less above the solution.
• 2. Freezing point depression
• a. Lower vapor pressure causes a lower
  temperature to freeze the solvent
• b. Solute particles also interfere with
  crystal formation
• c. Electrolyte (ionic) solutes have a greater
  effect due to disassociation into ions making
  more particles
• Sugar- 1 particle NaCl2 CaCl2 --3
• 3. Boiling point elevationsame cause as
  freezing point depressionalso solute particles
  interfere with vaporization

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Homework 10b

• CYU p 238 all
• p. 243 ff 6, 8, 12, 14, 18, 19,
• 24, 26, 28, 32, 37, 38

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Acids and Bases

• Definition Theories Presently Held
• 1. Bronsted-Lowry
• a. Acid is a proton(H) donor
• b. Base is a proton acceptor
• c. Explains all bases, but not all substances
  which act as acids
• 2. Lewis Theory
• a. Acid is electron-pair acceptorattracts
  elements with exposed electron pairs
• b. Base is electron pair donor (has exposed
  electron-pair)
• c. Explains how substances like Fe3 can become
  acids

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Common Definitions

• Acids conduct electricity in solution, react with
  active metals, sour taste, change blue litmus to
  red
• Bases conduct electricity in solution, feel
  slippery, have bitter taste, turn red litmus blue
• Some substances act as multiple acids since they
  have more than one acid H
• --polyprotic H2SO4 H3PO4

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Acid Base Strength

• 1. Strong acids completely ionize in
  solution
• HCl HBr HI HNO3 H2SO4 HClO4
• 2. Weak acids only partially ionize
• HC2H3O2 H2CO3 H3PO4
• 3. Strong bases have large attraction for
  protons
• OH- PO4-3 NH2-
• 4. Weak bases have small attraction for protons
• NH3 C2H3O2- NO2-

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Naming Acids

• If acid has no oxygen in its formula, it is
  binary
• a. Start the name with hydro-
• b. Add ic ending to the name of other element
  or ion
• c. Add the word acid
• HCl hydro chlor ic acid
• H2S -- hydrosufuric acid
• If acid has oxygen in its formula, it is an
  oxyacid
• a. Name the acid from the name of the
  polyatomic ion
• in itDO NOT NAME THE HYDROGEN!!!
• b. Add ic if the ion ends in ate
• c. Add ous if the ion ends in ite
• H2SO4 sufur ic acid (SO4-2 is sulfate)
• HNO2 nitrous acid (NO2- is nitrite)

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Neutralization of Acids With Bases

• 1. Acid plus base makes salt plus water
• HCl NaOH ? NaCl H2O ? typical example
•  
• 2. The reaction cancels both acid and base if
  concentrations are equal

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Ionization of Water

• H2O ? ? OH- H
• 1. Water is both weak acid and weak base
• 2. Equilibrium constant K for this reaction
  becomes Kw HOH- since H2O is pure liquid
• 3. Kw is constant at room temperature in pure
  water and equals 1 x 10-14 since
  HOH1x10-7

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Measuring Acid Base Concentrations

• pH Scale
• 1. Hydrogen ion concentrations can be measured by
  electric current flow or by the affect on certain
  indicators.
• 2. pH scale was developed to easily measure H
  by taking its negative log.
• pH -log H H10-pH
• 3. Acids have pH lt7 Bases ha pHgt7 Neutral
  pH7 whereH 1x10-7

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Homework 11a

• CYU p 257 all
• CYU p 260 all
• p 263ff 2, 13, 16, 17, 20

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Titrations

• Measure acid or base by combining a known
  quantity of one with a continually measured
  volume of the other. The pH is monitored until an
  indicator changes or pH meter measures neutral
  condition.
• MaVa MbVb

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Normality in Acids and Bases

• Polyprotic acids have more H so their molar
  concentration have more equivalent than
  monoprotic acids. These must be measured by
  normality to get equal effect

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pH and Body Systems

• pH has serious effects on biological materials if
  it is out of correct range
• a. Enzymes work only in specific pH ranges
• b. pH out of normal range can indicate disease
  of injury

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Buffers

• pH changes in biological situations can be very
  dangerous
• Buffers protect against changes in pH
• Best systems have a weak acid or base and a salt
  of that acid or base
• HC2H3O2 and NaC2H3O2
• NH3 and NH4Cl

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Buffers

• D. Blood buffer system is based on H2CO3 ,
  HCO3- and CO2
• 1. Too high CO2 causes acidosis (p H in blood
  too low)caused by
• a. Hypoventilation b. Emphysema c. Heart
  failure
• 2. Too high H caused by
• a. Diabetes b. Kidney failure c. Acid
  drugsaspirin or acid foods
• 3. Too low CO2 causes alkalosis (blood pH too
  high)caused by
• a. Hyperventilation b. High fevers c.
  Hysteria
• 4. Too low H caused by
• a. Severe vomiting losing acid from stomach
• b. Kidney disease

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Homework 11b

• p. 263ff 21, 22, 26, 28, 30