Brief review of important concepts for quantitative analysis

1
Brief review of important concepts for
quantitative analysis
CHM 235 Dr. Skrabal

• Some important units of quantification
• Units for expressing concentrations in solids and
  liquids
• Concentration-dilution formula

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Fundamental SI units

• Remember the correct abbreviations!

Mass kilogram (kg)
Volume liter (L)
Distance meter (m)
Temperature kelvin (K)
Time second (s)
Current ampere (A)
Amount of substance mole (mol)
Luminous intensity candela (cd)
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Some other SI and non-SI units
Length angstrom (Å)
Force newton (N)
Pressure pascal (Pa), atmosphere (atm)
Energy, work, heat joule (J)
Power watt (W)
Electric charge coulomb (C)
Electric potential volt (V)
Electric resistance ohm (?)
Electric capacitance farad (F)
Temperature degree Celsius (C)
degree Fahrenheit (F)
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Some common prefixes for exponential notation
1012 tera (T)
109 giga (G)
106 mega (M)
103 kilo (k)
10-1 deci (d)
10-2 centi (c)
10-3 milli (m)
10-6 micro (µ)
10-9 nano (n)
10-12 pico (p)
10-15 femto (f)
10-18 atto (a)
Remember the correct abbreviations!
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Commonly used equalities

• 103 mg 1 g milli thousandth
• 1 mg 10-3 g
• 106 µg 1 g micro millionth
• 1 µg 10-6 g
• 109 ng 1 g nano billionth
• 1 ng 10-9 g
• 1012 pg 1 g pico trillionth
• 1 pg 10-12 g

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Concentration scales

• Molarity (M)
• Molality (m)

• Molarity is a temperature-dependent scale
  because volume (and density) change with
  temperature.
• Molality is a temperature-independent scale
  because the mass of a kilogram does not vary with
  temperature.

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Concentration scales (cont.)

• Formality (F)

• Formality is sometimes used to express the
  concentration of substances, such as
  electrolytes, acids, and bases, that turn into
  different species in solution.
• For example
• 0.1 M NaCl ( 0.1 F NaCl) gives 0.1 M Na and
  0.1 M Cl- in solution
• 0.5 M HCl ( 0.5 F HCl) gives 0.5 M H and 0.5 M
  Cl- in solution

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Concentration scales (cont.)

• Weight / weight (w/w) basis
• (w/w)
• ppt (w/w)
• ppm (w/w)
• ppb (w/w)
• ppt (w/w)

? percent
? ppt parts per thousand
? ppt parts per million
? ppt parts per billion
? ppt parts per trillion
This scale is useful for solids or solutions.
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Concentration scales (cont.)

• Weight / volume (w/v) basis
• (w/v)
• ppt (w/v)
• ppm (w/v)
• ppb (w/v)
• ppt (w/v)

? percent
? ppt parts per thousand
? ppt parts per million
? ppt parts per billion
? ppt parts per trillion
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Concentration scales (cont.)

• Volume / volume (v/v) basis
• (v/v)
• ppt (v/v)
• ppm (v/v)
• ppb (v/v)
• ppt (v/v)

? percent
? ppt parts per thousand
? ppt parts per million
? ppt parts per billion
? ppt parts per trillion
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Concentration examples

• Concentrated HCl
• Alcoholic beverage
• Color indicator for titrations

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Concentration example (wv)

• What is the concentration, on a (wv) basis, of
  vanadium in a solution that contains 281.5 mg/L
  of vanadium?

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Concentration scales (cont.)

• Parts per million, billion, trillion are very
  often used to denote concentrations of aqueous
  solutions

Note ppt parts per trillion
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Concentration scales (cont.)

• It is important to memorize
• 1 part per million (ppm) 1 mg / L
• 1 part per billion (ppb) 1 µg / L
• 1 part per trillion (ppt) 1 ng / L

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Concentration examples

• Conversion of molarity to ppm
• Solution of 0.02500 M K2SO4

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Concentration examples

• What is concentration (in ppm) of K in this
  solution?
• Solution of 0.02500 M K2SO4

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Concentration-dilution formulaA very versatile
formula that you absolutely must know how to use

• C1 V1 C2 V2
• where C conc. V volume
• M1 V1 M2 V2
• where M molarity
• Cconc Vconc Cdil Vdil
• where conc refers to the more concentrated
  solution and dil refers to the more dilute
  solution. Note that you can use any units you
  want for conc. and vol. as long as they are the
  same on both sides of the equation.

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Concentration-dilution formula example

• Problem You have available 12.0 M HCl (conc.
  HCl) and wish to prepare 0.500 L of 0.750 M HCl
  for use in an experiment. How do you prepare
  such a solution?
• Cconc Vconc Cdil Vdil
• Write down what you know and what you dont know

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Concentration-dilution formula example

• Problem You have available 12.0 M HCl (conc.
  HCl) and wish to prepare 0.500 L of 0.750 M HCl
  for use in an experiment. How do you prepare
  such a solution?
• Cconc Vconc Cdil Vdil
• Cconc 12.0 mol L-1 Cdil 0.750 mol L-1
• Vconc ? Vdil 0.500 L
• Vconc (Cdil)(Vdil) / Cconc
• Vconc (0.750 mol L-1) (0.500 L) / 12.0 mol L-1
• Vconc 3.12 x 10-2 L 31.2 mL

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Concentration-dilution formula example

• Great! So how do you prepare this solution of
  0.750 M HCl?
• Use a pipet or graduated cylinder to measure
  exactly 31.2 mL of 12.0 M
• Transfer the 31.2 mL of 12.0 M HCl to a 500.0 mL
  volumetric flask
• Gradually add deionized water to the volumetric
  flask and swirl to mix the solution
• As the solution gets close to the 500.0 mL
  graduation on the flask, use a dropper or squeeze
  bottle to add water to the mark
• Put the stopper on the flask and invert 20 times
  to mix