Chem Lab Final Exam

uncertainty

measurement that shows how well something is known;

TC

made to contain (will contain the exact amount)

TD

made to deliver (made to deliver exact amount)

meniscus

curved surface where you read the volume

look at lowest graduation, then divide that by two

how do you determine uncertainty

volumetric

what type of glassware has to have the uncertainty given to you

implicitly

show all values in decimal place where uncertainty lies (ex: 67.0mL)

explicitly

show all values in decimal place where uncertainty lies AND stating uncertainty (ex: 67.0548g +/- 0.0001g)

graduated pipets

type of pipet that is calibrated and convenient for max capacity

volumetric pipet

pipet that delivers a single fixed volume of liquid

buret

used in titrations, to accurtely deliver a specific volume, or to help you measure that specific volume

blue; blue

you want the bunsen burner to have a ___ gas with a ___ inner cone

uncertainty, personal/human error, random error, and systematic error

what are the 4 types of errors

personal/human error

you, the experimenter, made a mistake

accuracy and percision

what does human error effect?

random error

caused by unknown and unpredictable changes in a measuring isntrument or in the environmental conditions

meter fluctuation

when using a balance, the last decimal place will fluctuate due to current, which adds to random error

percision

a measure of the reproducibility of an experiment and quantifies random error

1/2 range and standard deviation

what are the two ways of quantifying percision

1/2 range

2 or less trials, use ____ to quantify percision

standard deviation

3+ trials, use _____ to quantify percision

(maximum trial - minimum trial)/2

the formula for 1/2 range is....

squareroot of ( add all (average-trial squared))/ (amount of trials-1)

the formula for standard devation is...

systematic error

occurs when there are flaws in the measuring device which results in measurements being too high or too low, always in the same direction

accuracy

what does systematic error effect

accuracy

how close you come to an accepted value

[(experimental value-accepted value) / (accepted value)] x 100

the formula for %error or %difference is..

%error or %difference

what can you use to quantify systematic error

mixture

formed when 2 or more substances that don't react chemically are united

homogeneous (aka solutions)

appears uniform throughout, cannot see individual components

heterogeneous

not uniform throughout, as you can see the individual components

decantation, filtration, evaporation, extraction, and sublimation

different types of physical methods of separation

extraction

separation of a substance form mixture by preferentially dissolving that substance in a suitable solvent

evaporation

involves heating a solution to remove the solvent

sublimation

proces wehre solid passes directly to the gaseous state without the appearance of the liquid state

decantation

process of separating a liquid from a solid by gently pouring the liquid from the solid so as not to dsturb the oslid

sediment

name for a solid that comes out from decanting

supernatant liquid/ supernate

name for the liquid during decanting

filtration

process of separating a solid from a liquid by means of a pourous substance, a filter, which allows the liquid to pass through but not the solid

residue

the solid separated during filtration is called_____

filitrate

liquid that passes through the filter during filtration is called _____

gravity and vacuum

two types of filtration

AB + CD --> AD + CB

what is a double displacement reaction

mass of compound divided by mass of mixture, all multiplied by 100

how do you find percent component

mass of all compounds added then divided by the mass of the mixture, then all multiplied by 100

how do you find percent recovery

100%

what percent recovery do you want

gas chromatography

process that permits separation of a mixture into its components as a result of differences in rates at which the individual components of the mixture mitigate through a stationary medium under the influence of the mobile phases

mobile adn stationary

what are the two phases in gas chromatography

mobile phases

phase that uses gas and liquid in gas chromatographhy

stationary phases

phase that uses a pourous/granular solid and thin film abosrbed on a solid and paper

carrier gas

something that pushes along during gas chromatography

capillary column

real fine glass column

stationary

which phase has little interaction?

mobile

which phase has more interaction

slower

solutes that are more attracted to the stationary phase will move _______ as they get pushed along the column

retention time

injection to time it comes off; used to identify a component

peak area

area underneath the peak directly proportional to concntration

to figure out how many peaks is on the chromatogram

what can you use retention times for

to determine concentration of components

what can peak area be used for

emperical formula

shows teh smallest whole number ratio in which the atoms combine to form a compoud

molecular formula

formula that gives the actual number of atoms in a molecule

law of definite proportions

combining ratio of elements in a particular compound is constant regardless of the method of preparation or source

law of multiple proportions

when the same elements combine to form 2 different compounds, the two compounds will hav differetn mass ratios

convert mass to moles, divide by the smallest number of moles to find the ratio

how can you calculate emperical formula from mass?

absorption

moleules ability to absorb a photon of light at a particular wavelength

Colorimeter/Spectrophotometer

machine that produces wavelengths in the visible spectrum 375nm to 900nm

monochromator

selects particular wavelength of light and sends it out the sample cell with an intensity

detector

sits on teh other side of the saple cell to pick up how much light is being transmitted through the solution

%transmittance (%T)

corresponds to the % of light being transmitted through the sample

all light is being transmitted, no light is being transmitted

100% transmittance means _____ and 0% means ______

absorbance

how much is being absorbed by the molecule

Beer's Law

law that states the amount of energy absorbed or transmitted by a solution is proportional to the solution's molar absorptivity and the concentration of solute.

Stoichiometry

quantitative study of reactants and products in a chemical reaction

photometric titration

process where concentration of one reactant is held fixed, and the concentration of a second reactant is systematically varied while the product formation is monitored through absorbance

equivalence point

the point where just the right amount of both compounds reaction is called

combination reaction

occurs when two substances combine to form a compound A+B->AB

decomposition reaction

occurs wehn a compound breaks apart to form 2 or more products AB->A+B

single displacement reaction

occurs when one element displaces another element from a compound A+BC->AC+B

redox reaction

occurs when the oxidation state of one or more of the substances changes

oxidation (+)

loss of electrons

reduction (-)

gaining of electrons

reducing agent

element going through oxidation

oxidizing agent

element going through reduction

ion combination reaction (also metathesis, double displacement, preipitation, acid base reactions

AX+BY (two aqueous solutions)->AY+BX (forms a percipitate, gas weak or non-electrolyte)

law of concervation of matter

mass is neither created or destroyed

mass of final divided by mass of initial, all multiplied by 100 (we want 100% yield!! if less, that means we lost some mass along the way)

how do you find percent yield

limiting reaction

reagent that is used up firt in the reaction

titration

technique of accurately measuring the volume of a solution required to react with another reagent

standardization

process of determining the exact concentration of a solution

endpoint

point during titration when a color change occurs

autocatalytic

produces its own catalyst

Kinetic Theory of Matter

all matter consists of tiny particles which are in continual state of motion

gas pressure

results form a force exerted by a gas per unit of a surface area on an object

pressure, temp, volume, and moles

four variables for gases are _____

Boyle's Law

as volume decreases, pressure increases and vice versa

PV=PV

equations for Boyle's Law is_______

Gay-Lussac's Law

as temp increases, so does pressure and vice versa

P/T=P/T

equation for Gay-Lussac's Law is_____

Charles' Law

as temp increasesm so does volume and vice versa

V/T=V/T

equation for Charles' Law______