lab exam stuff
4e-7. 7.5e-14. 4.97e-19
A photon has a wavelength of 400. nanometers (nm). What is the length in meters?What is the frequency of this photon? what is the energy of this photon?
tetrahedral, sp3, bent
Based on the Lewis structure for H2O, consider the following.the electron geometry is __ and the hybridization is ____ and the molecular geometry is__________
CH2Cl2, PCl3
Based on your Lewis structures for the postlab assignment, which molecules below have a three dimensional structure?
C2H6
Based on your observations during the lab, which molecules below have a three dimensional structure?
.145 M
Data has been collected to show that at a given wavelength in a 1 cm pathlength cell, Beer's Law for the absorbance of Co2+ is linear. If a 0.135 M solution of Co2+ has an absorbance of 0.350, what is the concentration of a solution with an absorbance of 0.375?
absorbance measured by the spectrometer
Define the terms in the formula: A = ε l c. definition of A
concentration, in mol/L, of the sample solution being measured
Define the terms in the formula: A = ε l c. definition of c
open flame, hydrochloric acid
In the flame test experiment, you will be working with two types of hazard. Which are they?
The x- and y-axes should be labeled with units as well as quantities.Concentration is plotted on the x-axis. Absorbance is plotted on the y-axis.The command for getting an equation is "Add Trendline" in Microsoft Excel.
In this experiment, a calibration curve, often called a Beer's Law plot, will be made. A calibration curve should have which of the following attributes?
CN:3 sp
SCN- bond order and hybridization
SO:1.5 SO:1.5 sp2, bent
SO2 bond order, hybridization, shape
Some hydroxide (OH − ) compounds are not soluble.
Select any exceptions you found to the charge rule.
trigonal planar, sp2, trigonal planar
The electronic geometry of CH2O about the central atom is ___, the hybridization of the central C is ___, and the molecular geometry is __
trigonal planar, sp2, bent (120)
The electronic geometry of SO2 about the central sulfur atom is ___, the hybridization of the central S is ___, and the molecular geometry is ___
% difference = ((theoretical value − actual value) × 100%) / theoretical value.
The equation for percent error is:
4.49e14, 2.97e-19
The orange in fireworks is often due to the emission of light from Ca2+. If the primary wavelength is 668 nm, what are the frequency and energy of the light? (Enter your answers in scientific notation
lattice
The ordered arrangement of particles is called_______
allows more air (oxygen) into the flame
Twisting the sleeve to open the holes (baffles) above the base of the burner does which of the following?
1/8, 1, 2
Use the Body-Centered Cubic Cell Solid State Model to answer the following questions. Noting as before that the corner of the unit cell is defined by the nucleus of this atom, how much of this atom is inside the unit cell?Focus on the layer 2 atom. How much of this atom is inside the unit cell?How many total atoms are inside the unit cell?
.01
Volumes obtained with volumetric flasks, pipettes, and burets are recorded to the nearest ___ ml
Dilute a known volume of stock solution into a known volume of liquid.Dissolve a weighed amount (known mass) of solid into a known volume of liquid
What are the standard ways to make a solution of known concentration?
simple
________cubic unit cells have identical particles on all corners of the cube.
body centered
___cubic unit cells have identical particles on all corners, and in the center.
if structure of solid is not repetitive
amorphous
bigger
anions are ______ than the elements they form
yellow green, Ba2+
barium chloride, BaCl2. flame color and ion responsible for flame color
yellow-green, Ba2+
barium nitrate, Ba(NO3)2. flame color and ion responsible for flame color
orange-red, Ca2+
calcium chloride, CaCl2. flame color and ion responsible for flame color
orange red, Ca2+
calcium nitrate, Ca(NO3)2 flame color and ion responsible for flame color
smaller
cations are ____ than the elements they form
green, Cu2+
copper(II) chloride, CuCl2, flame color and ion responsible for flame color
green, Cu2+
copper(II) nitrate, Cu(NO3)2, flame color and ion responsible for flame color
solid, aqueous
dissolution reactions of a precipitate go from ___ to ___
yes
do Ag and Pb form s precipitate with Cl-
yes
does Mg2+ form a precipitate with OH, carbonate, and phosphate
linear, sp, linear
for C2H2 the electron geometry, the hybridization, and molecular geometry
trigonal planar, sp2, trigonal planar
for C2H4 the electron geometry, the hybridization, and molecular geometry
tetrahedra;, sp3, tetrahedral
for C2H6 the electron geometry, the hybridization, and molecular geometry
tetrahedral, sp3, tetrahedral
for CH4 the electron geometry, the hybridization, and molecular geometry
corner are divided by 8 , edge ones are divided by 4, and center one is just one and face ones are divided by 2. if two in the middle they are divided by two.
how do you calculate corner and center sites and face sites on face centered
labeled container
in the solubility rules It is a good idea to have a _____ n the work area to collect waste during the experiment.
discarded in a large waist container designated by your instructor
in the solubility rules lab All of the solutions prepared in this experiment should be _________
a small test tube
in the solubility rules lab If we cannot clearly see a reaction in the well plate, we should repeat it in ______
the gird or the solution already in the well. it can contaminate the reagent when its returned to the bottle
in the solubility rules lab The dropper should not be allowed to touch ______. If the dropper does touch one of these, __________
cations, toxic, ingested, washed well with soap and water
in the solubility rules lab some of the ___ are __. they should not be ____.If they are spilled on the skin, the area should be _____
three, is not a good idea to
in the solubility rules lab the instructions say to use ____ of each test solution in the well plate. it is probably ______ use more
deep red, LI+
lithium chloride, LiCl flame color and ion responsible for flame
pale violet, K+
potassium chloride, KCl flame color and ion responsible for flame
pale violet, K+
potassium nitrate, KNO3 flame color and ion responsible for flame
yellow, Na+
sodium chloride, NaCl flame color and ion responsible
yellow Na+
sodium nitrate, NaNO3 flame color and ion responsible
insoluble
soluble or insoluble based on lab trends AgBr
soluble
soluble or insoluble based on lab trends Na2SO4
insoluble
soluble or insoluble based on lab trends Pb(OH)2
insoluble
soluble or insoluble based on lab trends Pb3(PO4)2
bright red, Sr2+
strontium chloride, SrCl2 flame color and ion responsible
bright red, Sr 2+
strontium nitrate, Sr(NO3)2 flame color and ion responsible
unit cell
the _______ is the smallest repeating three-dimensional array that includes the stoichiometry of the compound as given by its empirical or molecular formula.
r=(2)^.5/4(a)
what is the radius equation for body centered
a=2r
what is the radius equation for simple cubic
simple cubic
what structure is cesium chloride appeared to be arranged in
body centered
which one is more void body centered or simple cubic
OH-, CO32-, PO43-
which solution of AL3+ created a precipitate:Cl-, ClO4-, OH-, CO32-, SO42-, PO43-
OH-, CO32-, SO42-, PO43-
which solution of Ca2+ created a precipitate:Cl-, ClO4-, OH-, CO32-, SO42-, PO43-
OH-, CO32-, PO43-
which solution of Mg2+ created a precipitate:Cl-, ClO4-, OH-, CO32-, SO42-, PO43-
OH-, CO32-, SO42-, PO43-
which solution of Sr2+ created a precipitate:Cl-, ClO4-, OH-, CO32-, SO42-, PO43-
linear, sp, linear
Based on the Lewis structure for N2O, consider the following. (a) The electronic geometry about the central nitrogen atom is ___, the hybridization of the central N is ___, and the molecular geometry is ___
tetrahedral., sp3, trigonal bipyramidal
Based on the Lewis structure for NH3, consider the following.. The electron geometry is __ the hybridization is ______ and the molecular geometry is _______
SO3 NO2-
Based upon your Lewis structures for the postlab assignment, which molecules below have multiple Lewis resonance structures that are equal?
A = ε l c.
Beer's Law
1.5 sp2
C6H6 bond order and hybridization
CO:2 CH:1 CH:1, sp2, trigonal planar
CH2O bond order, hybridization, shape
CH:1 x4, sp3 tetrahedral
CH4 bond order, hybridization, shape
1.3 sp2
CO32- bond order and hybridization
20 10 5
Calculate ER, VE, and SP for the formula C2H2 (ER = Electrons Required to give all atoms except hydrogen an octet and hydrogen a duet; VE = Valence Electrons available to all the atoms; SP = Shared Pairs of electrons: SP = 1/2(ER − VE)).
24 12 16
Calculate ER, VE, and SP for the formula C2H4 (ER = Electrons Required to give all atoms except hydrogen an octet and hydrogen a duet; VE = Valence Electrons available to all the atoms; SP = Shared Pairs of electrons: SP = 1/2(ER − VE)).
ER 28 Correct: Your answer is correct. VE 14 Correct: Your answer is correct. SP 7 Correct: Your answer is correct.
Calculate ER, VE, and SP for the formula C2H6 (ER = Electrons Required to give all atoms except hydrogen an octet and hydrogen a duet; VE = Valence Electrons available to all the atoms; SP = Shared Pairs of electrons: SP = 1/2(ER − VE)).
ER 20 Correct: Your answer is correct. VE 12 Correct: Your answer is correct. SP 4 Correct: Your answer is correct.
Calculate ER, VE, and SP for the formula CH2O (ER = Electrons Required to give all atoms except hydrogen an octet and hydrogen a duet; VE = Valence Electrons available to all the atoms; SP = Shared Pairs of electrons: SP = 1/2(ER − VE)).
ER 12 Correct: Your answer is correct. VE 8 Correct: Your answer is correct. SP 2 Correct: Your answer is correct.
Calculate ER, VE, and SP for the formula H2O (ER = Electrons Required to give all atoms except hydrogen an octet and hydrogen a duet; VE = Valence Electrons available to all the atoms; SP = Shared Pairs of electrons: SP = 1/2(ER − VE)).
ER 24 Correct: Your answer is correct. VE 16 Correct: Your answer is correct. SP 4 Correct: Your answer is correct.
Calculate ER, VE, and SP for the formula N2O (ER = Electrons Required to give all atoms except hydrogen an octet and hydrogen a duet; VE = Valence Electrons available to all the atoms; SP = Shared Pairs of electrons: SP = 1/2(ER − VE)).
14, 8, 3
Calculate ER, VE, and SP for the formula NH3 (ER = Electrons Required to give all atoms except hydrogen an octet and hydrogen a duet; VE = Valence Electrons available to all the atoms; SP = Shared Pairs of electrons: SP = 1/2(ER − VE)).
ER 24 Correct: Your answer is correct. VE 18 Correct: Your answer is correct. SP 3 Correct: Your answer is correct.
Calculate ER, VE, and SP for the formula SO2 (ER = Electrons Required to give all atoms except hydrogen an octet and hydrogen a duet; VE = Valence Electrons available to all the atoms; SP = Shared Pairs of electrons: SP = 1/2(ER − VE)).
absorption and emission
Color in a substance arises from which two closely related processes?
face-centered cubic > body-centered cubic > simple cubic
Comparing the "atom densities" of all three cubic unit cells, rank them in packing efficiency, with the most efficiently packed cell listed first.
face centered cubic
Comparing this structure (face-centered cubic) to the last structure (body-centered cubic), which one appears to have less void volume?
while rinsing the wire with acid
When cleaning the wire between flame tests, most of the cleaning is accomplished when?
pathlength of light through the cell
Define the terms in the formula: A = ε l c.. definition of l
molar absorptivity, a constant unique to that substance at that wavelength
Define the terms in the formula: A = ε l c.definition of ε
NH3 CH4
Did the model set and computer models help you identify the molecular shape better than the Lewis structures? In particular, which molecules have a three dimensional structure. (Select all that apply.)N2O NH3 SO2 H2O CH4 CH2O
No. For SCN−, formal charge indicates the best resonance structure has a S-C double bond and a C-N double bond. This places the negative charge on the more electronegative atom, N. However, the computer model and reality indicate the best structure is has a S-C single bond and a C-N triple bond.
Do your observations agree with what you have learned about formal charge?
6
Focus on the central, blue sphere of layer 2. How many colorless spheres are in contact with it?
6
Focus on the central, colorless sphere of layer 1. How many blue spheres are in contact with it? This is its coordination number.
The Lewis structures for CH2O, H2O, NH3 and CH4 closely match the computer model., Multiple Lewis structures can be drawn for the SO2 molecule. The computer model S-O bond lengths indicate that the true structure is an average of the Lewis structures.Multiple Lewis structures can be drawn for the N2O molecule. The computer model N-N and N-O bond lengths indicate that the true structure resembles only one of the Lewis structures.
For each of the six molecules, how did your Lewis structures compare to the molecular models on the computer? Select the statement(s) below that most closely agree with your observations. (Select all that apply.)
The computer model of NH3 had a slightly smaller H-N-H bond angle than predicted by hybridization.In general, the molecules shape and model bond angles were close to the predicted values of 180, 120, and 109 degrees.The computer model of H2O had a slightly smaller H-O-H bond angle than predicted by hybridization.
For each of the six molecules, was your Lewis structure a good and accurate representation of the molecule's actual shape? Select the statement(s) below that most closely agree with your observations. (Select all that apply.)
2, 50.7, 17.2,34.3,67.7
Given that a solid crystallizes in a body centered cubic structure that is 3.70 Å on each side, answer questions (a)-(e). (1 Å = 1. 10-10 m.)How many total atoms are there in each unit cell?What is the volume of one unit cell in Å3?Assuming that the atoms are spheres and the radius of each sphere is 1.60 Å, what is the volume of one atom in Å3Therefore, what volume of atoms are in one unit cell?Based on your results for questions (b) and (d), what is the packing efficiency of the solid expressed as a percentage
OH:1 OH:1 sp3 bent
H2O bond order, hybridization, shape
1 and 1
How many colorless and green spheres are inside the unit cell? for cesium chloride
There is not enough information to determine how this would have changed the calculated unknown concentration, but it would not be the same.
How would the results have changed if a cell with a different pathlength had been used for measuring the unknown than the calibration standards?
Rinse them in running water.
If one spills hydrochloric acid on one's hands, what is the FIRST thing one should do
The results would have been the same.
If the spectrometer had been set to a different wavelength to measure absorbances (one where the copper would have absorbed more or less light), how would that have changed the results?
For SCN−, the best resonance structure has a S-C single bond and a C-N triple bond. This agrees with computer model, which shows a long S-C bond length and a short C-N bond length.
If there was a molecule with unequal Lewis resonance structures, which structure is the best according to the computer model?
flourite
In Part B, a model of_______ a mineral form of calcium fluoride, will be assembled.
soluble
In general, are compounds containing ammonium ions (NH4+ ) or ions from Group 1 on the Periodic Table soluble or insoluble?
soluble
In general, are compounds containing an ion with either a +1 or −1 charge soluble or insoluble?
insoluble
In general, are compounds containing carbonate (CO32− ) anion soluble or insoluble?
insoluble
In general, are compounds containing phosphate (PO43− ) anion soluble or insoluble
soluble
In general, are compounds containing sulfate (SO42− ) anion soluble or insoluble?
The calculated unknown concentration should be the same.
In this experiment, you used a 1 cm pathlength cell for all measurements. If a 0.1 cm pathlength cell had been used for all the measurements, how would that have changed the results (concentration of the unknown)?
no
Looking back at your data in Part A, are all single bonds the same length?
2.53e22 1.27e22 2
Many metals pack in cubic unit cells. The density of a metal and length of the unit cell can be used to determine the type for packing. For example, sodium has a density of 0.968 g/cm3 and a unit cell side length a of 4.29 Å. (1 Å = 1. 10-8 cm.)How many sodium atoms are in exactly 1 cm3?How many unit cells are in exactly 1 cm3How many sodium atoms are there per unit cell?
MgBr2(s) → Mg2+(aq) + 2 Br−(aq) cation anion
MgBr2 solids to water will produce ions according to the dissolution reaction below.
NN: three NO: one, sp linear
N2O, bond order, hybridization, shape
NH:1 NH:1 NH:1 sp3 trigonal pyramidal
NH3 bond order, hybridization, shape
Food and beverages are never permitted in labs., There will be no waste material in this experiment
Select all responses which correctly address safety issues in the Molecular Modeling lab.
The usual rules about appropriate clothing and safety glasses must be observed.. Food and beverages are never permitted in labs.
Select all responses which correctly address safety issues in the Solid State Modeling lab.
As the charge on an ion increases, its compounds are more likely to be insoluble., Coulomb's law, E = (q1 · q2) / (ε · r2), accounts for trends in solubility.Metals with high electronegativities are likely to form insoluble compounds.
State the general rules that relate the solubility of an ionic compound with the charges on the ions of which it is composed.
the gas flow
The valve on the bottom of the burner controls which of the following?
There will be no waste material in this experiment.
The wastes in the Solid State Modeling experiment should be disposed of in the following way.
1/8, 1/2, 4
Use the Face-Centered Cubic Cell Solid State Model to answer the following questions.Noting as before that the corner of the unit cell is defined by the nucleus of this atom, how much of this atom is inside the unit cell.Now focus on a layer 2 atom. How much of this atom is inside the unit cell?How many total atoms are inside the unit cell?
1/4, 1/8, 1
Use the Simple Cubic Cell Solid State Model to answer the following questions. how much of the atom is inside the shaded region? The corner of a cubic cell such as this one is defined by the center (nucleus) of the atom at the corner. How much of this atom is above the nucleus and inside the shaded region (i.e. inside the unit cell)? How many total atoms are inside the unit cell
face centered cubic, face centered cubic, 4, 4
Use the Sodium Chloride Structure Solid State Model to answer the following questions. Focus on only the colorless spheres. What type of cubic structure do they appear to be arranged in? Focus on only the blue spheres. What type of cubic structure do they appear to be arranged in?How many colorless adn blue spheres are inside the unit cell
contain , 0.1
Volumetric flasks are built to ____________ a known volume of liquid to an accuracy of about _____________ % of the flask's capacity.
flush the affected area with water
What actions should you take if you spill copper(II) sulfate solution on yourself?
pants that extend to the ankles, shirt and pants that overlap 6",a shirt that covers the shoulders (has sleeves), shoes that cover heels and toes
What clothing is appropriate for the laboratory?
there were no exceptions
What exceptions did you find to the Group 1 Rule?
K+ and NH4+ does not form a precipitate
What exceptions did you find to the carbonate ion rule?
K+, and NH4+
What exceptions did you find to the phosphate ion rule?
Sr2+ and Ca2+ forms a precipitate
What exceptions did you find to the sulfate ion rule?
the tip of the inner, dark blue cone
What is the hottest part of a Bunsen burner flame?
sp
What is the predicted hybridization at an atom which is surrounded by two double bonds?
An electron emits energy and it makes a transition to a lower energy orbital.
What process is occurring when the color appears in the flame?
An electron absorbs energy and it makes a transition to a higher energy orbital.
What process is occurring when the solution is heated?
It should be dumped in a beaker labeled "waste copper" on ones bench during the experiment. It should be disposed of in the bottle for waste copper ion when work is completed.
What should be done to waste solutions containing copper ion?
crystalline
When an ordered arrangement of particles extends over a long distance in a solid, the material is considered_____
The area above the burner must be clear before it is lit.The area near the burner should be clear of paper and other flammables.The burner must never be left unattended.The substance being heated should never be pointed at people.If the flame blows out, the gas must be turned off, because gas could accumulate and an explosion could occur. Flammable liquids should never be heated with a Bunsen burner.
When working with a Bunsen burner, which of the following precautions must be observed?
irritant and toxic
Which hazards are associated with copper(II) sulfate?
Lithium ions emitted longer wavelength photons than sodium ions since the lithium ions emitted light at a lower frequency.
Which ion emitted photons with the longer wavelength in the visible region: Li+ or Na+
Copper(II) ions emitted higher energy photons than strontium ions since the copper(II) ions emitted light at a shorter wavelength.
Which ion emitted the higher energy photons in the visible region: Cu2+ or Sr2+?
Barium ions emitted lower frequency photons than potassium ions since the barium ions emitted light at a lower energy.
Which ion emitted the lower frequency photons in the visible region: Ba2+ or K+?
O22-
Which of the following anions will you NOT be studying in the Solubility Rules experiment? OH −, ClO4−,Cl −,NO3−,O22−,CO32−,PO43−,SO42−
Li
Which of the following cations will you NOT be studying in the Solubility Rules experiment? Li+,Fe3+,Sr2+, Ca2+, Mg2+, NH4+, Al3+
all ionic species in the reaction mixture are shown
Which of the following is NOT true about a net ionic equation?A liquid product is indicated with its formula followed by (l). Only ionic species which participate in the reaction are shown. A solid product (precipitate) is indicated with its formula followed by (s). All ionic species in the reaction mixture are shown. Spectator ions are not shown in the equation. A gaseous product is indicated with its formula followed by (g).
C6H6, CO32-
Which of the three molecules had Lewis resonance structures that were equal?
Because the concentration is calculated from the absorbance, the errors should be the same for both.
Why would you expect the percent differences for the absorbance to be similar to the percent differences for the concentration in each part of the experiment?
face centered
_______ cubic unit cells have identical particles on all corners, and on all faces of the cube.
minimum, a large volume
in the solubility rules lab, use the ____ amount of water possible, to avoid creating ______ of waste solution
c
ion solution color color absorbed A violet yellow B orange blue C yellow violet D blue orange Which ion has the highest energy absorption maximum?
deep red, Li+
lithium nitrate, LiNO3
to deilver
most pipettes are built to ______ of a known volume of a liquid
OH-, CO32-, PO43-
which solution of Zn2+ created a precipitate:Cl-, ClO4-, OH-, CO32-, SO42-, PO43-
none
which solutions of K+ created a precipitae: Cl-, ClO4-, OH-, CO32-, SO42-, PO43-
none
which solutions of NH4+ created a precipitate: Cl-, ClO4-, OH-, CO32-, SO42-, PO43-
.185
y=.185x+.232; Calculate the molar absorptivity (ε) of Cu2+ at 620 nm given that the cuvettes used in lab had a pathlength of 1.00 cm.
.042
y=.185x+.232; If a solution has an absorbance of 0.100 in a 1.00 cm pathlength cuvette, what would the absorbance be in a cuvette of 0.42 cm pathlength cell?
1.10 M
y=.185x+.232; What is the concentration of a solution with an absorbance of 0.435?
.275
y=.185x+.232;What absorbance would you expect from a solution of 0.2340 M concentration
