CHEM 1148

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Cards (222)

  • International system of units
    • Referred to as SI units Metric system
    • i.e. decimal Seven SI base units from which all other units can be derived
  • International system of units (SI) is the standard system of units used in science and technology

    Length = meter = m
    Mass = kilogram = kg
    Time = second = s
    Temperature = kelvin = K
    Amount of substance = mole = mol
    Electric current = ampere = A
    Luminous intensity = candela = cd
  • International system of units
    Prefixes commonly used, e.g. km, m, cm, mm, nm
    10^6 = mega = M
    10^3 = kilo = k
    10^-1 = deci = d
    10^-2 = centi = c
    10^-3 = milli = m
    10^-6 = micro = (mew)
    10^-9 = nano = n
    10^-12 = pico = p
  • International system of units
    Prefixes commonly used, e.g. km, m, cm, mm, nm
  • International system of units
    Units derived from SI base units
  • International system of units Units derived from SI base units
    Area = Length squared
    Volume = Length cubed
    Density = Mass per unit volume
    Speed = Distance travelled per unit time
    Acceleration = Speed changed per unit time
    Force = Mass times acceleration of object
    Pressure = Force per unit area
    Energy = Force times distance travelled
  • Units of Energy
    Energy : the potential or capacity to move matter
    • different types: heat, light, electrical, chemical, kinetic, potential
    • Chemical energy: energy concerning substances (kinetic and potential)
    • In a chemical reaction, chemical energy can: be converted to heat energy be used to break/make bonds
  • Units of Energy
    Ek = ½ mv2
    Ek = kinetic energy
    m = mass (kg)
    v = velocity (m/s)
    The SI unit for energy is kg • m2/s2 , more commonly known as Joule (J)
    Chemists also use calorie (cal) as a unit of energy
    • This is a non-SI unit of energy, originally defined as the amount of energy required to raise the temperature of one gram of water by one degree Celsius
    • 1 cal = 4.184 J
  • Units of Pressure
    Pressure is defined as the force exerted per unit area of surface
    Force = mass x constant acceleration of gravity; units are kg x m/s2

    Pressure = force / area
    Therefore, the units of pressure are (kg x m/s2 ) / m2
    = kg x m x s-2 x m-2 = kg x m-1 x s-2
    = kg / (ms2 )

    The SI unit of pressure is kg / (ms2 ), known as the Pascal (Pa)
  • Non-SI units of Pressure
    A common device to measure pressure is a manometer
    Measures the displacement of a liquid (e.g. mercury) inside a sealed vessel
    Pressure can be measured in millimetres of mercury (mmHg) (or Torr)
    A standard atmosphere (atm) = 101 325 Pa = 760 mmHg
    The bar and the millibar (mbar or mb) are also units of pressure Widely used in descriptions of pressure as 1 bar ≈ 1 atm
    1 bar = 100 000 Pa
    1 mbar = 0.001 bar = 100 Pa
  • Units of Temperature
    There are at least 3 temperature scales
    Science: Only Celsius and Kelvin are used Kelvin is the absolute temperature scale, i.e. zero
    Kelvin is the lowest temperature that can be obtained theoretically
  • Conversion between Temperature scales
    Celsius & Kelvin have equal size units, so it’s easy to convert between them
    • Celsius to Kelvin: K = ° C + 273
    • Kelvin to Celsius: ° C = K - 273
    Relationship between Celsius & Fahrenheit is more complicated:
    • Fahrenheit to Celsius: ° C = (°F - 32) / 1.8
    • Celsius to Fahrenheit: ° F = (1.8 x °C) + 32
    Typical room temperature is 20 ° C (or 293 K)
  • When we dissolve a substance in a liquid:
    • the substance is called the solute (smaller part)
    • the liquid used is called the solvent (larger part)
    The final product of this action is called a solution
    A homogenous mixture of 2 or more substances, i.e. the solute(s) and solvent(s)
    [homogenous mixture means all in the same phase, i.e. liquid (all dissolved)]

    Concentration refers to the quantity of solute in a standard quantity of solvent
    • Dilute = solute concentration is low
    • Concentrated = solute concentration is high
  • Typical expressions and their units
    • percentage (% w/w, %v/v, %w/v)
    • milliequivalents (mEq)
    • molarity (mol/L) or molality (mol/Kg)
    • grams per mL (g/mL)
    • mole fraction
  • Dimensional analysis (factor-label method)
    d = 15.0 g / 10.0 cm3 = 1.50 g/cm3
  • Volume is defined as length cubed, but m3 is too large a unit for normal lab work
    The more commonly used units are:
    Cubic decimetres (dm3 )
    Cubic centimetres (cm3 ) [also written cc]
    Traditionally, chemists use litre (L) as the unit of volume (unit of volume equal to a cubic decimetre) Most laboratory glassware is calibrated in litres or millilitres
    1 L = 1000 mL = 1000 cm3 = 1 dm3
  • The density of an object is its mass per unit volume
    d = m / V
    m = mass in g
    V = volume in cm3
    d = density in g/cm3
    e.g. if an object has a mass of 15.0 g and occupies a volume of 10.0 cm3
    d = 15.0 g / 10.0 cm3 = 1.50 g/cm3
  • Density is an important characteristic property of a material
    • Density varies with temperature and pressure
    • Can be used to ascertain the purity of a substance, e.g. gold
    • Used to calculate the volume of a liquid reagent rather than using its mass
  • A molecule is...
    An aggregate of two or more atoms in a definite arrangement held together by chemical bonds
  • Isotopes of an element...
    have nuclei with the same number of protons (the same atomic number), but different numbers of neutrons (different mass number)
  • Monoisotopic weight of an atom: Atomic weight

    The monoisotopic mass of an atom is equivalent to its mass number for the given isotope
    • The atomic mass of 12C is 12 amu & the atomic mass of 13C is 13 amu
    • Atomic weight is defined as the mass of a singular isotope
    • 1 atomic mass unit (amu) = 1 Dalton (Da)
  • Relative atomic weight is the abundance weighted average of isotopic masses
    • To calculate the atomic weight of an element we need to know how many isotopes it has and their natural abundance
  • The relative molecular mass (Mr or RMM) of a substance is also known as molecular weight (MW)
    Mr =
    • the mass of one molecule of that substance relative to the unified amu
    • the sum of all the atomic weights of all the atoms in a molecule
    • Mr = The molecular formula + relative atomic masses of elements in the molecule
  • The formula weight (FW) of a substance is often described as the same as the molecular weight (MW).
    Not strictly true as some substances have additional compounds present in their formula, i.e. more than one molecule, e.g. water of crystallisation
  • A mole is...
    • the quantity of a given substance that contains as many molecules of formula units as the number of atoms in exactly 12 g of carbon-12.
    Avogadro’s number (NA ) = 6.02 x 1023
  • The molar mass of a substance is the mass of one mole of that substance [units = in grams per mole (g/mol)]
    For all substances, the molar mass in grams is numerically equal to the formula weight in atomic mass units
    Ethanol has molecular weight of 46.1 amu ➔ molar mass 46.1 g/mol
  • If I have 10 g of ethanol, I have 0.217 moles of ethanol
    Number of moles (n) = Mass (g) / molar mass (g/mol) = 10 g / 36.1 g/mol = 0.217 moles
    n =m / Mr
  • Molar concentration is defined as the number of moles of solute dissolved in one litre (dm3 ) of solution
    Molarity (M) = Moles of solute / Litres of solution
    Molar concentration = Molarity = M has units mol L-1 (or mol dm-3 )
  • Qualitative analysis involves the identification of substances or species present in a material
    Quantitative analysis involves the determination of the amount of a substance or species present in a material
    Two common types are:
    • Gravimetric analysis: converting the species to a product that can be isolated completely and weighed, e.g. precipitation
    • Volumetric analysis is a method of analysis based on titration
  • Use of calibrated glassware 

    Do not dry in oven as this will alter calibration of the glassware.
    • When using calibrated glassware measure using the meniscus correctly to obtain an accurate volume
    • the meniscus is the curved surface of the liquid
  • Volumetric analysis is a method of analysis based on titration
    Titration is a procedure for determining the amount of a substance (A) present
    • by adding a carefully measured volume of solution of substance B (whose concentration is known) until the reaction between them is just complete
  • Diluting solutions
    Molarity (M) = Moles of solute/Litres of solution
    Moles of solute = Molarity (M) x Litres of solution
    • For the initial concentration and volume, the moles of solute = Mi x Vi
    • When we have diluted the initial solution we get the final concentration and volume, where the moles of solute = Mf x Vf
    • The number of moles of solute does not change between the initial and final solutions, only the concentration and volume do
    Mi x Vi = Mf x Vf
  • Diluting solutions
    If volume has doubled then concentration will have decreased by half as the number of moles of solute does not change.
    E.g. Moles of solute = 1.0 x 0.25 = 0.5 x 0.5 = 0.25 moles
  • Why is Chemistry important in Pharmacy?
    • The design of new drugs
    • The manufacture and quality control of known drugs
    • The formulation of drugs into preparations that can be administered to patients, e.g. dosage forms such as injections, tablets and creams
    • Understanding how drugs work at the molecular level (pharmacology)
    • Research in the pharmaceutical, pharmacological, biomedical and other health sciences
  • All matter can be broken down chemically into about 100 different elements This includes drugs, proteins, etc.
  • DNA - the genetic material
    • 4 bases: guanine, cytosine, adenine and thymine
    • Sugar phosphate backbone
    • 2 strands held together by hydrogen bonding
    • Holds the genetic instructions for the biological development of all forms of life
  • Dalton’s atomic theory
    • Elements are made of tiny particles called atoms
    • All atoms of a given element are identical
    • Atoms of a given element are different from those of any other element
    • Atoms of one element can combine with atoms of other elements to form compounds
    • Atoms are not created or destroyed in chemical processes
    • A chemical reaction simply changes the way the atoms are grouped together
  • Atomic structure
    Atoms contain a nucleus surrounded by electrons
    • Nucleus is tiny and dense
    • Contains protons (+ve charge) and neutrons (neutral)
    • Electrons (-ve charge) occupy a (relatively) large volume around the nucleus
  • Atomic structure
    Charge on proton = charge on electron
    • Neutral atoms have equal numbers of protons and electrons
    • If an atom gains an electron, it becomes negatively charged
    • If an atom loses an electron, it becomes positively charged
    The number of protons remains constant
  • Atomic structure: Properties of subatomic particles
    Particle Symbol Charge Mass (g) Relative mass
    Electron: e - -1 9.109 x 10-28 1
    Proton: p +1 1.673 x 10-24 1836
    Neutron : n 0 1.675 x 10-24 1839