CHM 2045 L UF Lab Exam

Percent error formula

calculated value minus expected value l value divided by expected value times 100

Find density given unknown concentration graphy y=mx+b

y is density and x is mass % so sub value of y to find x

Density formula

mass/ volume

Hydrate definition

crystalline compound in which one or more water molecules combine with formula unit of walt that loses water above 100c

% water= mass water lost/ mass hydrate times 100

Mass water lost=

unheated mass minus mass after heating

PH2=

ptotal - pvapor

Ptotal= patm-pfluid

h1d1=h2d2

p1v1/t1=P2V2/T2

Molarity= moles/volume in L

Q=

mCgDelta T Q is the symbol for heat transfer, m is the mass of the substance, and ΔT is the change in temperature. The symbol c stands for specific heat and depends on the material and phase

Lowest energy color

red

Smallest electronic transitions

lowest atomic #

Highest energy color is

violet

molality=

moles/kg

Calculate i=

mass particles/ moles compound dissolved

Accuracy -

A description of how close a measurement is to the true value of the quantity measured.

Precision -

a measure of how close a series of measurements are to one another

sig figs for addition and subtraction -

the result has the same number of decimal places as the measurement with the fewest decimal places

sig figs for multiplication and division -

the result has the same number of sig figs as the term with the least number of sig figs

density formula -

D=m/v

percent error formula -

|accepted value-measured value| / accepted value x100

how to take a proper measurement -

record the measured value plus one estimated digit

how to take a proper liquid measurement -

read from the bottom of the miniscus

mass percent of solute -

mass of solute/mass of solution x 100 ALSO mass of solute / (mass of solute + mass of solvent) x 100

independent variable is graphed on the -

x-axis

dependent variable is graphed on the -

y-axis

finding moles -

(total grams) / (molar mass) = moles

mass percent of water -

(grams of water lost) / (grams of hydrate before it was heated) x 100

reduction -

gaining electrons

oxidation -

loss of electrons

How does titration work? -

Fill a burette with a known volume of an alkali, at a known concentration. Make sure the acid is in an aqueous solution at a known volume, and get it into a beaker with a pipette. Add an indicator to the acid (phenolphthalein), and begin to drop the alkali in from the burette, until the solution has turned permanently pink, indicating that the acid is now neutral. Record the volume of alkali added.

Titrant -

A solution usually of known concentration that is used to titrate a solution of unknown concentration (added to the analyte)

Analyte -

Substance being analyzed, usually of unknown concentration

equivalence point -

the point at which the two solutions used in a titration are present in chemically equivalent amounts

end point of titration -

when the titration ends (the point at which the indicator changes color)

Ideal Gas Law -

PV=nRT (n is equal to the number of moles of the substance and R is the gas constant 0.082)

STP (standard temperature and pressure) -

conditions of 0.00°C (273 K) and 1 atm pressure

calorimetry equation -

q=mcdeltaT

Hess's Law -

the overall enthalpy change in a reaction is equal to the sum of enthalpy changes for the individual steps in the process

q of the system = -

-q surroundings

q of reaction = -

-q solution

specific heat of water -

4.184 J/gC

delta H of a reaction -

sum of delta H products - sum of delta H reactants

Beer's Law -

A=ebc

What does each letter represent in A=ebc -

A is absorbance, b is path length (length of cuvette in cm), e is molar absorbtivity, c is concentration

when volume of a solution changes, its new concentration can be determined by -

m1v1 = m2v2

rate = -

k[A]^m[B]^n

Energy of a photon equation -

E=hv where h=6.626E-34 and v=frequency

formal charge equation -

valence electrons - sticks and dots

The empirical formula of the hydrate can be found by determining x in the formula salt.xH2O. X is found by comparing moles of water lost to moles of anhydrous salt remaining:

(moles water)/(moles anhydrous salt) = x

Titrant:

the substance being added to the analyte. In this case the Ce4+ solution is the titrant, being added via micropipette. The titrant usually is of known concentration.

Analyte:

the substance being analyzed. Often of unknown concentration. In this case, the Fe2+ solution is the analyte.

Equivalence point:

the point at which the titrant and analyte are present in a stoichiometric equivalent ratio based on their reaction.

End point:

where the titration ends in reality. If you're using a visual indicator, this would be where you would observe the completion of the reaction. If using an indicator, you would choose one such that the end point is as close as possible to the equivalence point. This reaction is somewhat self-indicating - the color of the combined reagents should become slightly yellow as excess Ce4+ becomes present.

Titration curve:

this can be a pH vs volume curve, showing change in pH as titrant is added, for an acid/base reaction. Or, as in this case, it can be a graph of potential vs volume of titrant added. There are other options, as well, such as conductance vs volume.

The Ideal Gas Law has the formula:

𝑃𝑉=𝑛𝑅𝑇

R is the Gas Constan

t 0.08206

Pgas =

Patm - Pfluid.

The pressure exerted by a fluid due to gravity can be calculated by the equation:

𝑝=ℎ𝑑𝑔

1 atm mmhg

= 760 mmHg

1 atm torr

= 760 Torr

1 atm pa

= 101325 Pa

1 atm mbar

= 1013 mbar

Transmittance (T) is the fraction of light at a given wavelength that passes through a light-absorbing medium. Transmittance is defined as: T=I/Io

When no light is absorbed, I = ___ and A=0

I0 and A = 0.

Beer lambert law

absorbance= molar absopivity times distance in cm times concentration

These are usually strong electrolytes and can be expected to 100% dissociate in aqueous solution.

ionic

These are usually non-electrolytes. They do not dissociate to form ions. Resulting solutions do not conduct electricity.

molecular compounds

These are molecules that can partially or wholly dissociate, depending on their strength.

molecular acids

Formal Charge =

[# of valence electrons on atom] - [non-bonded electrons + number of bonds].

Vant hoff factor is

i