Chem 113 Final
a reaction rises to 22.1 Celsius to 25.3 Celsius, how many calories of heat were produced
(1.0 g/cal/Celsius) x (125 g) x (3.2 Celsius) = 0.400 kcal
ΔHf
-68.3 kcal/mole
STP conditions
0 degrees Celsius, 22.4 L
How many mL of 3.0 M HCI is required to prepare 250 mL of 1.0 M HCI by dilution?
250 mL x 1 M/ 3 m = 83.33 mL
What would the Pw be in torr if the height of a water column buret was 26.2 cm?
262 mm/13.6=19.265 torr
What safety rule do we bend?
Adding water to acid. HCI more dense than water, we get two layers. The trapped HCL diffuses down the buret and reacts with MG.
Why is it important to calculate the volume of "dry gas"?
In order to use the ideal gas law and Pwv is taken out.
Volume formula
length x width x height OR mass/density
Density units
liquid or solid= g/mL gasses= g/L
concentration of barium hydroxide=
moles(barium) / volume of BaOH2 used
If heat is lost to the surroundings, does it have a positive error, negative error, or no effect?
negative error
Pg=
Pb-Pwv-Pw
valence is equivalent to
oxygen state
pH1/2 =
pKa
pH
pKa = pKa + log [A-]aq/ [HA]aq
1000 mL
1 L
conversion factor for cm3 and to mL
1 because there is no difference
units of cal =
1 cal/g°c x g x °c
Density of water
1 g/mL
1 cm3=
1 mL = 1 g
How many electrons are involved in one equivalent of oxidation-reduction?
1 mole
one kcal =
1 nutritional calorie = 4.184 kj
density of water =
1.000 g/cm3
equivalent weight of hydrogen
1.008 g
1 kcal=
1000 calories
Number of Equivalents of H2
11.2 L @STP= 1 equivalent
Suppose that in a 10.0 mL sample of Ba(OH)2 the mass of the crucible with the precipitate was 17.550 g and the mass of the empty crucible (tare weight) was 17.410 g. Calculate the concentration of the Ba(OH)2 solution from this data.
17.550-17.410 = .140 g BaSO4/MW BaSO4 = .140g/233.4 g/mol BaSO4 = 5.998 x 10^-4 mol 5.998 x 10^-4 mol/ 0.010 L = .06 M Ba(OH)2
Given a 10.0 mL sample of the unknown Ba(OH)2 solution, calculate the concentration of the solution if it took 12.08 mL of a 0.0980 M H2SO4 to reach the equivalence point.
2.08 mL H2SO4 (0.0980 M H2SO4) = 10.0 mL Ba(OH)2 (x Ba(OH)2) 1.1834 = 10.0 (x) x = 0.118 M Ba(OH)2
Water is it's most dense at
4 degrees Celsius
specific heat of water
4.184
1 atm=
760 torr
Valence of Mg
= atomic weight/equivalent weight
Equilibrium
A state of balance
Beer's Law
A=[E*b*C] E= molar absorbance b=path's leght c=concentration
spectrophotometer
An instrument that measures the proportions of light of different wavelengths absorbed and transmitted by a pigment solution.
Why do some things have a high or low density?
Depends on how the molecules are arranged in space
What is the purpose of adding the hydroxyl amine hydrochloride in the solutions analyzed in this experiment?
Determine the iron present and reduce the Fe3+
(Spectrometric Analysis of Iron, Beers law) For the blank sample, the only reagent omitted is
Fe2+
Let HX represent the formula of a weak acid. Write a balanced chemical equation for the reaction of this weak acid with the strong base NaOH.
HX + NaOH --> NaX + H2O
Why is density important?
It identifies a substance
units of molar absorptivity
L mol ^-1 cm -1
Heat=
Mass x specific heat x DeltaT (temp change)
Why is molality used in the equation used to determine freezing point depression
Molality is not temperature dependent since the mass of the solvent remains constant.
Suppose lead (II) chloride got into your Ba(OH)2 contaminating it. What would happen? What about FeCl3
More H2SO4 would be required to be added to the unknown. This leads to a higher concentration of Ba(OH)2. FeCl3 is insoluble so there would be no effect.
density is dependent on
Temperature. Most objects expand (or increase volume) as they are heated which resulting in a decrease of density
What would happen to absorbance if the solution diluted from 1 M to 0.33 M?
The absence would decrease meaning the absorbance would become 1/3 of the solution diluted from 1 M to .33 M.
What color is the Cu(NH3)+
The color is dark blue. The maximum absorbance wavelength is 610 nm.
How would your value for equivalence weight be affected if some of the H2 gas produced during the Mg(s) reaction and acid escaped from the buret?
The equivalence would be higher because the same amount of Mg would result in H2.
Why does the introduction of a solute into a solution change the freezing point? How does the freezing point change?
The freezing point of a solution is always less than one of a solvent. The solutions temp. must be lower than the solvent for the freezing to occur.
Enthalpy
The heat content of a system at constant pressure. enthalpy tells how much heat and work was added or removed from the substance. Enthalpy is similar to energy, but not the same.
Where is the freezing point seen on the graph of temp vs. time of the Freezing Point depression lab?
The place where the graph levels off is the location of the freezing point. To be specific, its at the y intercept of the flat portion of the curve.
What would happen if MG ribbon were left out and a layer of magnesium oxide formed on it and not rubbed off with the steel wool?
The reaction would be slowed down because the MgO would prevent t the O2 from coming in contact with Mg.
Suppose the barium sulfate weighed in the crucible above was not completely dry. How would this affect the concentration calculated for the barium hydroxide solution?
The weight of the solution will increase. The concentration will be too high.
volume of a cylinder
V = πr2h
C2=
V1C1/V2
Volume HCI/NaOH added=
Vf-Vi= ΔV
Could a measured specific heat of an unknown but pure metal sample be used to help identify the metal? Why or why not?
Yes because metals have their own specific heat
Ka =
[H3O+][A-]/[HA]
Ksp equation
[products]/[reactants]
Density can be
a conversion factor
molar absorptivity (E)
a measure of how strongly the sample absorbs light at a particular wavelength.
If a weak acid is titrated with a strong base, will the equivalence point in the titration occur at above or below pH 7.0
above
Calorimeter
an insulated device used to measure the absorption or release of heat in chemical or physical processes
state functions
are path-independent
pH = pKa
at half-equivalence point in titration
Valence
atomic weight/equivalent
Δ
change
Convert 105.3 mm to H2O to torr
change of height (triangle) / 13.6
Calcium chloride used
density lab (2 solutions) one more dense than the other
extensive properties
depend on the amount of matter that is present
intensive properties
do not depend on the amount of matter present
a reaction rises to 22.1 Celsius to 25.3 Celsius is exothermic or endothermic
exothermic because the temperature was raised
Beer's Law
explains the relationship between absorbance, at a given wavelength and concentration, A = εbc
If HX represents the formula of a weak acid, what is the formula of the conjugate base of HX?
formula of the conjugate base of X-
Kf=
freezing point depression for the solution
order of density
gas=least dense, liquid more dense, solid=most dense
Why do ice cubes float in water?
ice cubes are less dense than water
A Rock Weighs 143 g in air 82 g in H2O What is the mass of H2O displaced? Volume H2O displaced? Density of the rock?
m = 143 m = 82 change of mass = 143-82 = 61 g of water V = m/d = 61/1 = 61 ml density of rock D = masS/V = 143/61 = 2.34 g /ml B) m = 28.102 g V = 6.25 ml m = 34.2 change of m = 34.2-28.102 = 6.098 D = masS/V = 6.098/6.25 = 0.97568 g/ml
Heat given off determined by
mass * specific heat * temperature change (Q=mc(deltaT))
Density
mass/volume
Quantitive Analysis
measures traits or behaviors that can be numerically calculated
Qualitive analysis
measures traits or behaviors that non-numerically
Net HCI to titrate soda ash
mol HCL - mol NaOH
molality
moles of solute/mass of solvent (kg)
ppm
parts per million
Piece of PVC
should be equal to the density of the solution in the density lab
Ksp =
solubility product
Law of Dulong and Petit
specific heat divide by 6.4 is approximate atomic mass of that metal
enthalpies of a reaction are
state functions
enthalpy of formation
the change in energy when one mole of a compound is assembled from pure elements
Enthalpy of formation (ΔHf)
the heat given off when one mole of a substance is prepared from its constituent element in their standard states.
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
specific gravity
the ratio of a substance to the density of water.
equivalent weight
the weight of the substance that will react with or produce one mole of hydrogen
Average % of Na2Co3 in sample=
trial 1% + trial 2 %/2
Pw=
Δh/13.6
symbol for wavelength
λ
