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Accuracy
How close a measured value is to the true value.
Precision
How close a set of measured values are to each other.
Resolution
The smallest distinguishable change that can be measured accurately.
Random error
Errors that occur due to chance and include fluctuations in measurements.
Systematic error
Errors caused by the measuring device itself, consistently above or below the true value.
Dilution equation
C1V1 = C2V2, where C is concentration and V is volume.
Beer’s law
States that the amount of light absorbed or transmitted is an exponential function of the concentration of the absorbing substance and the length of the path of light through the sample.
o 𝑇 =10^−𝑎𝑏𝑐 or −log10𝑇 = 𝑎bc
o T = transmittance
o b = path length
o a = constant depending on the substance absorbing the light
o c = concentration
o A = absorbance: A= - log T
Colorimetry
Measurement technique used to determine the concentration of a particular compound in a colored solution.
Spectrophotometers
Devices that accurately measure the amount of light absorbed or transmitted.
Electromagnetic radiation
Energy that can be described as existing in small packets (photons) or in terms of waves.
Spectroscopy
The study of the interaction of electromagnetic radiation with matter.
White light
A sample containing all wavelengths of visible light.
Absorption
Occurs when electrons move from low to high energy state absorbing energy.
Emission
Occurs when electrons move from an excited state to ground state, releasing energy.
Chromatography
Separation technique that uses two phases of different polarity to separate components of a mixture.
Stationary phase
A porous substance used in separation techniques like chromatography.
Mobile phase
Fluid that can flow through the porous stationary phase in chromatography.
Paper chromatography
Technique where nonpolar components have higher affinity for the mobile phase and travel further.
Rf
Distance spot traveled divided by distance solvent travels from the spotting line.
Reverse phase chromatography
Chromatography where the stationary phase is less polar than the mobile phase.
Solution
A homogeneous mixture of two or more substances.
Solute
Substance present in a smaller amount in a solution.
Solvent
Substance present in larger amount in a solution.
Dissolution
Process involving the breaking of bonds and formation of new associations in solution.
Solubility
The concentration of solute in a saturated solution at a specific temperature.
Water
A polar covalent molecule.
Dissociation
Occurs when a solute breaks apart into smaller components.
Electrolytes
Presence of charged ions in solution that allows it to conduct electricity.
Non-electrolyte
A solute that does not conduct electricity.
Acidic cation
Cations that react with water to produce H+ ions.
Neutral cation
Cations that do not react with water.
Convection
Mass transport by moving fluid.
Diffusion
Spontaneous decrease in concentration differences due to random molecular motion.
Like dissolves like
The principle that polar solvents dissolve polar solutes, and nonpolar solvents dissolve nonpolar solutes.
Qualitative analysis
Finding out what elements or substances are present in a sample.
Quantitative analysis
Determining how much of each component is in a sample.
Arrhenius acid
Any substance that produces H+ when added to water.
Arrhenius base
Any substance that produces OH- when added to water.
Bronsted-Lowry acid
Proton donor.
Bronsted-Lowry base
Proton acceptor.
Lewis acid
Electron pair acceptor.
Lewis base
Electron pair donor.
Acid-base indicator
Substance that changes colors at different pH values.
Hygroscopic
Refers to solids that attract water from the atmosphere.
Titration
Technique used to determine the concentration of an unknown solution by slowly adding a solution of known concentration.
Equivalence point
The point at which an acid is completely reacted with a base in titration.
Molarity equation
M1V1 = M2V2, for calculating concentrations in titration.
Back titration
Determining the concentration of an analyte by reacting it with an excess reagent, then titrating the remaining excess.
Calorie
Amount of energy required to raise the temperature of 1 g of water by 1°C.
Food calories
The relationship between energy and our bodies, where 1000 calories = 1 food calorie = 1 Calorie = 1 kcal.
Calorimetry
Experiment determining energy released or absorbed during a reaction based on temperature change.
Calorimeter
Device used to measure the change in temperature due to a chemical reaction.
Specific heat
Amount of energy required to raise the temperature of 1 g of a substance by 1°C.
q=mCT
Equation relating heat gained or lost (q) to mass (m), specific heat (C), and temperature change (T).
