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