Section D Flashcards
Dalton’s Atomic Theory
All matter is made up of atoms
Atoms of a specific element are identical to each other, but different from atoms of any other elements
Compounds are combinations of atoms of two or more different elements
In chemical reactions, atoms are combined, separated or rearranged
They are never created or destroyed
IONS
An atom containing an equal number of protons and electrons is electrically neutral
Gain of electron —— convert the atom to a negative ion – known as Anion
Loss of electron —— convert the atom to a positive ion – known as Cation
Positively charged ion – usually metals
Negatively charged ion – usually nonmetals
( ionization)
An atom gain or loose electrons to create a stable outer valence shell
Ionic Bond
An ionic bond is a chemical bond that involves a metal and a nonmetal ion
Atoms either losing or gaining negatively charged electrons, reacting to form ions
Positive ions (metals) are attracted to negative ions (nonmetals)
In naming simple ionic compounds, the metal (cation) is always first, the nonmetal (anion) second
Flint glass (soda lime):
Inexpensive, low resistance to heat and chemicals. Used to make disposable test tubes
Borosilicate glass:
Nonreactive with most chemicals, high thermal (heat) resistance glassware
Used for most lab glassware
Quartz/Silica glass:
Very expensive, contains only silica quartz with excellent optical qualities
Used for high precision work – spectrophotometry cuvettes, microscope lens
Volumetric pipette
Used for critical/accurate measurements
Calibrated to deliver “TD” a single volume
Has a bulged out portion (bulb) in the middle
Serological/Graduated pipette
Calibration marks to the tip
Etched ring around the top – last drop must be blown out
Mainly used for preparing serial dilutions
Transfer total capacity or partial volumes
Mohr pipette
Not calibrated to the tip
Do not drain beyond last calibration marking
Acids
Substance that release hydrogen ion (H+) as the only cations, when dissolved in water/aqueous solution
(loss of protons / proton donors)
When using acid and water, acid is slowly added to water
Bases
Substances that produce hydroxide ions (OH-) when dissolved in water
Salts
ionic compounds composed of cations and anions with an electrically neutral product
An acid and a base react to form a salt
Electrolytes
Solution that carries (conducts) electricity
Acids, bases, and salts form electrolytes because they produce ions when dissolved in H2O
Ions act as moving electrical charges and carry electricity
Electrodes
electrode is an electric conductor / cell that is referred to as either an anode or a cathode
Opposites attract Anode is (usually) positive Cathode is (usually) negative
Non Electrolytes (Sugars)
Do not produce ions
Dissolve as molecules
Do not conduct electricity
pH
pH is a measure of the acidity or alkalinity/basicity of a solution
A measurement of hydrogen ions in solution
(Mathematically) pH is the negative logarithm of the activity of hydrogen ions concentration
alkaline is basic
Low pH many H+ —> acidic solution
High pH few H+ —> basic solution
A pH decrease of 1 indicates that the solution is 10 times more acidic.
pH of Body Fluids
gastric juices 1.0 – 2.0 (strong acid)
blood 7.35 - 7.45 (weak base)
bile 7.8 - 8.6 (weak base)
urine 4.5 – 8.0 (weak acid
Buffer Solution
A solution that will maintain a constant pH when a small amount of acid or base is added to it
It is composed of a mixture of a weak acid or base and a salt of the acid or base
When acid is added, a buffer will absorb H + using the salt portion
When a base is added, a buffer will release H+ from the acid portion; this will neutralize the OH-
Analytic Reagent (AR)
ultra pure - used for clinical analysis
Pharmaceuticals:
Tested for toxic substance United States Pharmacopeia (USP) National Formulary (NF) Canadian Pharmaceutical (CP) Used to manufacture drugs Can be used in most clinical lab
American Chemical Society (ACS)
- high standard of purity
HPLC water – Solvents manufactured specifically for use with HPLC instruments. Meet all ACS specifications. Submicron filtered
Technical/Commercial grade
low purity Never used in chemical labs
Lab Grade
used in educational labs
Concentration
the amount of solute per unit of solution/solvent
Molarity (M)
Number of moles of solute per liter (1000 mL) of solution
A mole is the gram molecular weight of an element or a compound
Moles/liter (mol/L)
Normality (N)
one gram equivalent of a solute per liter of solution
Colloids:
Mixture in which one substance is divided into minute particles
Tiny particles suspended in a liquid
Colloids do not pass through membranes and will not settle
Examples of colloids –
Fog, smoke, homogenized milk
Osmolality
Concentration of all particles in a fluid solution
Usually expressed as osmol/kg or Osm/kg
Distillation
distilled water - organic materials removed
Ion exchange (anion/cation resin)
deionized water - not very pure or sterile
Reverse osmosis
pressure force water through semi permeable membrane
Ultra filtration
remove particles , pyrogens and micro-organisms
Type 1
Water of highest purity
Type 11
Less pure, for general lab procedure
Distilled
Type 111
Least pure, used for general washing
Tap water
Water in the body
60% water contain within the cells as intracellular fluids
40% extracellular fluids (interstitial fluid in tissues and blood plasma)
Best Accuracy for pH meter
A minimum of three standards are required for a calibration curve
a pH meter cannot be calibrated without a standardized buffer
Covalent bonds
occur when two or more nonmetal atoms come together and share valence electrons to become stable
Each atom donating half of the electrons to be shared (equal sharing)
Covalent bonds are strong, they do not break when in water
Compounds containing covalent bonds are nonelectrolytes
Electronegativity
attraction of an atom for electrons in a covalent bond
The attraction or affinity of an atom for electrons in a chemical bond (covalent)
Elements with high electronegativity attract electrons more easily
Non metals are more electronegativity than metals
Metals lose electrons more easily
Most covalent bonds involve atoms of non- metallic element
Nonpolar covalent bond
Two atoms with the same electronegativity will share the bonding electron pairs equally
Polar covalent bonds
If two bonded atoms have different electronegativity, the bonding pairs of electrons will be shared unequally
They are different atoms, difference in electronegativity, different charge at both ends of the molecule
Hydrogen Bonds
The Hydrogen bond is weaker than covalent or ionic bonds
Chemical indicator
any substance that gives a visible sign, usually by a colour change, of the presence or absence of athresholdconcentration of a chemical, such as an acid or an alkali in a solution
Used in titration to identify the endpoint of an acid-base reaction
Used to gauge pH values
A pH indicator
change color over a narrow range ofpH valuesin solution
pH indicators display different colors between certain pH limits
Example:
Blue litmus paper turns red in acidic conditions, and red litmus paper turns blue under basic conditions
Accuracy
how close a measure of measurement is to the actual or true value
Precision
how close or how repeatable the results are
Gaussian Distribution
when many sets of data fit one particular curve when graphed
+/- 1 SD
68.3%
+/- 2 SD
95.5%
+/- 3 SD
97.7%
What the % in the guassian curve known as
confidence intervals or empirical rule
Average
also known an measure of central tendency
mean - sum of all numbers divided by the number of items in the set
Median
also a measure of central tendency
middle of a set of numbers after placing them from highest to lowest
if two then divide
Mode
also a measure of central tendency
the number that occurs most frequently
bimodal when one number occurs twice
Measure of variation
to describe how spread out or scattered a data set is consists of range and standard deviation
Range
difference between highest and lowest number
Standard deviation
measure of precision
Coefficient of variation
CV
used to compare precision of results when changing instruments
the more precise instrument will have a lower CV
Outliers on Levey Jennings
values lying outside the established range
Trend
six or more consecutive plots in one direction either up or down
-weakening light source
can be saw toothed
sudden failure of light source
Shift
when 6 or more values fall on/above or on/below the mean line
Systemic error
trend or shift
Random Error
deviation away from calculated mean
anything outside of 3SD is unacceptable
1 2 S rule
one value above +2s or below -2s but less than 3SD
Warning Rule - Red Flag Rule
Dont need to immedieately reject it
1 3S
If one point falls outside the 3SD range
must reject
2 2 S
if two consecutive points on the same side of hte mean exceed 2 sd but not 3SD
must reject
R4S
if the difference between two consectutive data points is 4SD with one above 2SD and one below -2SD
Rejected
41S
if 4 consecutuive points exceed 1SD on the same side of the mean
rejected
10x
if 10 consecutive points fall on the same side of the mean
