Chem Lab Final

density is an ____ property

intensive —> remains constant

% error equation

|theoretical - actual| / actual

% error is also a measure of…

accuracy

x bar

mean

n

number of measured values in a series

s

standard deviation

X_i

individual measured values

x-axis

independent variable; cause

y-axis

dependent variable; effect

theory

well-sustained explanation of some aspect in nature

null hypothesis

no significant difference

alternative hypothesis

contradicts null

dependent variable

what is observed/measured

independent variable

what is manipulated

hydrate

crystalline compound in which one or more water molecules are combined with each formula unit of salt

mass % of water

mass water lost / mass hydrate x 100%

equivalence point

point of inflection on the graph —> where there is a sharp increase in slope

solving for slope

y₁ - y₂ / x₁ -x₂

equivalence point given the second derivative graph

where the center of the dip crosses the x-axis

the titrant in a titration

• what is being added —> “is titrated with”

• solution of known concentration that is added to the analyte

what is the analyte in a titration

• the solution that something is added to —> “a solution of ____”

• substance in a solution whose concentration is being determined

titration

technique used to determine the concentration of a substance (analyte) in a solution by reacting it with a known volume and concentration of another substance (titrant)

equivalence point

• point in a titration where the stoichiometrically equivalent amounts of the analyte and titrant have reacted

• where titrant = analyte

equivalence point of a simple titration curve

can you determine where the first derivative’s maximum point is?

NO

the second derivative is ____ at the equivalence point

zero

solving for equivalence point given the second derivative equation

set y = to 0

absolute zero

temperature at which the volume of a gas would be zero according to Charles’s law

Barometer

device used to measure atmospheric pressure

Dalton’s law of partial pressures

total pressure of a mixture of ideal gases equals the sum of the partial pressures of the component gases

ideal gas

hypothetical gas whose physical properties are perfectly described by the gas laws

kinetic molecular theory

theory based on simple principles and assumptions that effectively explain ideal gas behavior

manometer

• device used to measure the pressure of a gas trapped in a container

• P_gas = P_atm - P_fluid

• the fluid is mercury

• pressure of the fluid is equal to the difference in height of the fluid level in units of millimeters

pressure exerted by a fluid due to gravity

• p = hdg

• h = height of fluid

• density of fluid

• 9.81 m/s²

vapor pressure

• pressure exerted by a vapor in equilibrium with its liquid in a closed container

standard VP of water in mmHg

23.78

P_gas =

• P_atmosphere - P_{water column}

• P_{water column} = height water (mm) / 13.6 —> ____ mmHg

scientific law

statement that describes a consistent and universal relationship observed in nature; describes what happens

endpoint

point in a titration where the reaction between the analyte and titrant is complete

oxidation

process in which an element’s oxidation number is increased by loss of electrons

reduction

process in which an element’s oxidation number is decreased by a gain of electrons

• oxidizers

• oxidizing hazard

• flammable

• self-reactive

• self-heating

• flammable gas

• corrosive

• burns skin

• damages eyes

• carcinogen —> cancer causing

• toxicity in many aspects to humans

toxic to aquatic environment

• acutely toxic

• can cause death

gases under pressure

• acutely toxic —> harmful

• irritant to skin, eyes, or respiratory tract —> flip it upside down and it looks like an i for irritant

• hazardous to ozone layer

• explosives

• self reactives

• red: flammability hazard

  • higher the number, the bigger the hazard

• yellow: instability hazard

  • higher the number, the more unstable it is

• blue: health hazard

  • the higher the number, the more of a hazard to human health

• white:

  • OX = oxidizing

  • SA = simple asphyxiants

  • W = reacts with water violently

thermal energy

kinetic energy associated with random motion of atoms and molecules

work

force acting on something, causing it to move

heat capacity

quantity of heat (q) an object absorbs or releases when it experiences a temperature change

specific heat capacity

quantity of heat required to raise the temperature of 1 g of substance by 1°C.

electromagnetic radiation

energy propagated through space in the form of electromagnetic waves

wavelength

distance between two consecutive points in a wave that are in phase

frequency

number of oscillations or cycles of a wave that occur in a unit of time

amplitude

maximum displacement or height of a wave from its equilibrium position

quantization

process of restricting or quantifying certain properties, such as energy levels, to discrete values rather than allowing a continuous range

absorbance

• measure of the amount of light absorbed by a substance as it passes through a sample

• concentration of an absorbing substance in the sample and is often employed to quantify the concentration of solutes in a solution

Spectrophotometer

• scientific instrument used to measure the intensity of light at different wavelengths in a sample

• operates on the principle that certain compounds absorb light at specific wavelengths

parts of a spectrophotometer

• light source

• a monochromator or diffraction grating to select specific wavelengths

• a sample holder

• detector

transmittance

measure of the amount of light that passes through a substance or medium; expressed as a percentage

Transmittance of light through a solution decreases exponentially with…

distance or concentration

when no light is absorbed…

• I = I₀

• A = 0

higher concentration means more/less absorbance?

MORE

how is asprin produced?

salicylic acid and acetic anhydride (condensation rxn)

the melting point of a substance depends on…

the intermolecular force and purity of a substance

TLC process

• piece of silica gel adsorbed onto a surface (the stationary phase) is spotted using a spotting tool (a thin capillary tube) near its base with solutions of compounds and mixtures

• Before spotting, a ruler is used to draw a pencil line near the base of the silica and tick marks are drawn along the line to guide spotting

1. watch glass covering the beaker

2. beaker

3. TLC plate

4. developing solvent

5. filter paper

The TLC plate is typically made out of…

silica which is very polar

More ____ compounds are more attracted to the TLC plate and their travel is hindered

polar

R_f

• distance traveled by analyte / distance traveled by eluent

• distance from origin to center of spot / distance from origin to solvent front

  • always measure from the center of the spot

impure vs. pure melting point

impure melting point is lower, and the range is wider than that of a pure substance

why is vacuum filtration better then gravity filtration?

It allows for faster and more efficient separation of solids from liquids

inductive reasoning

process of drawing a general conclusion from specific observations

3 most common categories of hazard

agent, condition, and activity

teratogen

can cause birth defects

lachrymator

irritate eyes and cause tearing

pyrophoric

ignite spontaneously in air