Chem lab exam

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).