chem lab exam
A buret should be read to which nearest mL?
0.01 ml
2 MnO4− + 5 H2O2 + 6 H+ → 2 Mn2+ + 5 O2 + 8 H2O (a) What is the stoichiometry of MnO4− to H2O2?
2:5
Which of the following is a true statement?
390 nm blue light is higher in energy than 610 nm yellow light
Use what you learned in lab about atoms in cubic structures to answer the following questions about a solid whose crystal structure was found to have atoms "C" in edge and center sites and "D" in the face sites of a cubic unit cell.How many "C"s are there in a unit cell?How many "D"s are there in a unit cell?
4 and 3
A student finds two unlabeled flasks of clear liquids. One is believed to be 0.1 M NaCl and the other to be 0.1 M NaClO3. What is a quick way of determining what is in each flask?
Add AgNO3 solution to each, AgCl will precipitate from NaCl.
causes staining on skin
Ag
This ion forms a precipitate with HCl. The precipitate re-dissolves when base is added and re-precipitates when acid is added.
Ag+
What is the strongest oxidizing agent?
Ag+
Which species has the lowest energy-unfilled or partially-filled orbitals?
Ag+
What process is occurring when the solution is heated?
An electron absorbs energy and it makes a transition to a higher energy orbital.
What process is occurring when the color appears in the flame?
An electron emits energy and it makes a transition to a lower energy orbital.
Which ion(s) remain in the supernatant from step 5? (Select all that apply.)
Ba2+
Which of the three molecules had Lewis resonance structures that were equal? (Select all that apply.)
C6H6 CO32−
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.)
CH4 NH3
What is the chemical formula for cesium chloride?
CsCl
State a general rule about what happens to the pH of acidic or basic solutions when they are diluted with pure water.
Diluting a strong acid results in a lower concentration of hydronium, which increases the pH. Diluting a strong base results in a lower concentration of hydroxide, which decreases the pH.
Which of the following equations correctly gives the cell potential?
Ecell = Ecathode − Eanode
Based upon the solubility rules in the introduction, which ion(s) remaining in the supernatant from step 4 will precipitate in basic solution? (Select all that apply.)
Fe3+
With what compound, element, or ion did the magnesium react? Give its chemical formula. (Omit states-of-matter from your answers.)
H2O
corrosive and irritating vapors
HCl, H2SO4, HNO3, NH3
HX and HY are weak acids, but HX is a stronger acid than HY. What result would you expect if you measured the pH of 0.1 M solutions of HX and HY?
HX would have a lower pH than HY.
Which element in the experiment has the fewest lines in its spectrum?
Li (lithium)
At what positions do the black lines appear, relative to the emission spectrum?
Most or all of the black lines appear where the emission spectrum had colors.
A student has two solutions of 0.10 M acid labeled just as A and B. The pH of one solution was found to be 1.02 and the other 4.73.
One is a strong acid and one is a weak acid.
If an unknown solution containing only one cation forms a white precipitate upon the addition of HCl and a white precipitate upon addition of H2SO4, which of the following ions must be present? (See the Table of Solubility Rules.)
Pb2+
Select any exceptions you found to the charge rule. (Select all that apply.)
Some hydroxide (OH − ) compounds are not soluble.
The pH of 0.066 M HC2H3O2 is 2.96. Why don't the two equimolar solutions of HCl and HC2H3O2 have the same pH? (Select all that apply.)
The Ka of HC2H3O2 is smaller than that of HCl, so at equilibrium the concentration of H3O+ ions in a HC2H3O2 solution is less than in a HCl solution of the same concentration; At equilibrium, the HC2H3O2 solution contains mainly undissociated HC2H3O2 and only small amounts of H3O+
Which statements below describe the changes that molecules undergo when heat is applied to a single phase? (Select all that apply.)
The heat energy causes an increase in the bond vibrations within the molecule.The heat energy is used to increase the kinetic energy of the molecules, raising the temperature
Given that the elements emit light in narrow frequency bands, rather than a color continuum, which of the following statements must be true?
The phenomenon causing the emission is quantized rather than continuous.
Based upon the pH you measured, which statement is accurate?
The reaction of hydrogen carbonate as a base with water is more extensive because the measured pH is greater than 7.
Choose all of the following that are true about the endpoint of the titration.
The solution will change to faint pink for at least 30 seconds, The amount of analyte equals the amount of titrant added.
Choose the most efficient and accurate way to prepare a sample containing 0.75 moles of iron (Fe) atoms.
Weigh 41.89 grams of iron.
What conclusions can you draw about C-C bond order and bond length for the series C2H6,C2H4, and C2H2? Select the statement below that most closely agrees with your observations.
When comparing bonds between the same two elements, as bond order increases, bond length decreases.
What is the strongest reducing agent?
Zn
Which species has the highest energy-filled or partially-filled orbitals?
Zn
There are two solutions on the shelf, 0.1 M Ca(NO3)2 and 0.1 M NH4NO3. Some Na3PO4 is added to a sample of each. What happens next?
a Ca3(PO4)2 precipitate forms
Which two quantities are inversely proportional to one another?
frequency and wavelength
A chemical species that gets reduced during a chemical reaction:
gains electrons changes to a more negative oxidation state is an oxidizing agent has a low-energy unfilled orbital obtains electrons from a reducing agent
In the experiment on Le Châtelier's Principle, why must one be very careful when handling concentrated hydrochloric acid (12 M HCl)? (Select all that apply.)
highly corrosive, respiratory irritant
A solution's pH is a measure of what?
hydronium ion concentration
What happened to the pH when the 0.010 M HCl was diluted to 0.0010 M HCl? It increased.It decreased. It did not change.
increased
Cd3(PO4)2 soluble or insoluble
insoluble
The _______________ the Ksp value, the more product that is formed at equilibrium.The lower the charges on the ions in an ionic solid, the more ________________
larger, soluble
The ordered arrangement of particles is called
lattice
Simple cubic packing efficiency
lowest
In what order should the readings be listed in Data Table B2?
most negative to positive
Vinegar is listed as which of the following?
none listed
An alternate name for the simple cubic unit cell is the _____________ cell
primitive
The valve on the bottom of the burner controls which of the following?
the gas flow
A supernatant liquid could be described as which of the following?
the liquid remaining above a precipitate
What is the hottest part of a Bunsen burner flame?
the tip of the inner, dark blue cone
How are these colors related?
they are complimentary colors
Why is it important to "wash" a precipitate with water?
to remove soluble ions to prevent false tests later in the experiment
Some of the cations are ____________If they are spilled on the skin, the area should be _______________
toxic, washed will with soap and water
Based on the Lewis structure for SO2, consider the following. The electronic geometry about the sulfur atom is The orbital hybridization about the sulfur atom is which of the following? The molecular geometry about the sulfur atom is
trigonal planar sp2 bent 120
Cu2+ and Mg
will react
During lab, you observed an emission of green visible light from the Cu2+ ion. The literature reports emission of blue visible light from the Cu+ ion. Choose the statement(s) below that best explain this data. (Select all that apply.)
1- Increasing the effective nuclear charge on an ion results in energy levels that are closer together. 2-The Cu2+ ion has a greater effective nuclear charge than the Cu+ ion.
State the general rules that relate the solubility of an ionic compound with the charges on the ions of which it is composed. (Select all that apply.)
1- Metals with high electronegativities are likely to form insoluble compounds. 2-As the charge on an ion increases, its compounds are more likely to be insoluble. 3-Coulomb's law, F = k · (q1 · q2) / (𝜀 · r2), accounts for trends in solubility.
What exceptions did you find to the sulfate ion rule? (Select all that apply.)
1-Ca2+ forms a precipitate. 2-Sr2+ forms a precipitate.
When operating the centrifuge, students should do which of the following?
1-Centrifuge for approximately 30 seconds. 2-Make sure that the lid is completely shut and the safety knob is turned to engage the safety switch.
What should be done with waste materials in the Qualitative Analysis experiment? (Select all that apply.)
1-During the experiment, wastes should be kept in a labeled beaker at the bench. 2-After the beaker is emptied, it should be rinsed with a little water, and the rinsings should be poured into the container. 3-All wastes should be put in the container on the side shelf.
What exceptions did you find to the carbonate ion rule? (Select all that apply.)
1-K+ does not form a precipitate. 2-NH4+ does not form a precipitate.
What exceptions did you find to the phosphate ion rule? (Select all that apply.)
1-NH4+ does not form a precipitate. 2-K+ does not form a precipitate.
What exceptions to the general solubility rules did you observe by mixing Ag+ with I−, and Pb2+ with I−? (Select all that apply.)
1-Pb2+ forms a precipitate. 2-Ag+ forms a precipitate.
When placing test tubes in the centrifuge, what are the best practices?
1-Place test tubes containing approximately equal volumes in opposite positions on the rotor. 2-Never put stoppers or other items in the centrifuge with your tubes.
Choose all the statements that correctly describe the policy for lab cancellations due to university closure. See the syllabus section of the Lab Manual.
1-Students may be provided with sample data or a video in order to complete the in-lab assignment.2-The student's in-lab grade may be composed of one less in-lab assignment. 3-Students are still responsible for the WebAssign prelab and postlab. 4-Labs are cancelled when the university is operating under the Adverse Weather Policy.
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.)
1-The Lewis structures for CH2O, H2O, NH3 and CH4 closely match the computer model. 2-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. 3-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, 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.)
1-The computer model of H2O had a slightly smaller H-O-H bond angle than predicted by hybridization. 2-In general, the molecules shape and model bond angles were close to the predicted values of 180, 120, and 109 degrees. 3-The computer model of NH3 had a slightly smaller H-N-H bond angle than predicted by hybridization.
When the centrifuge process is complete, students should do which of the following?
1-Using the eyehole on top, monitor the spinning rate and open the lid only after the rotor has slowed significantly. 2-Wait for the rotor to come to a complete stop before attempting to remove your test tubes.
If a student knows ahead of time that he/she must miss a lab for an excused event, he/she should...
1-arrange with the Lab Coordinator or TA to attend the same lab experiment at a different time during the week (procedures at CH102/CH202 Moodle at http://wolfware.ncsu.edu). 2-plan to have the missing in-lab score replaced by the final exam percentage divided by two if the student cannot attend an alternate lab during the week. 3-contact the instructor in advance.
If a student is absent due to sudden illness or emergency, he/she should...
1-contact the instructor as soon as possible and within 24 hours of the absence. 2-plan to have the missing in-lab score replaced by the final exam percentage divided by two if the student cannot attend an alternate lab during the week. 3-arrange with the Lab Coordinator or TA to attend the same lab experiment at a different time during the week (procedures at CH102/CH202 Moodle at http://wolfware.ncsu.edu).
If a student must miss TWO regular semester labs for excused events, he/she should...
1-plan on receiving an incomplete for the lab course. 2-be sure to have documentation for the absences.
What is the stoichiometry of NaOH to vinegar in the neutralization reaction?
1:1
What is the stoichiometry of HC2H3O2 to Ca(OH)2?
2:1
The structure below has thallium atoms in corner and face sites and fluorine in edge and center sites of a cubic unit cell.How many thallium atoms are there in a unit cell?How many fluorine atoms are there in a unit cell?
4 and 4
What would the approximate pH of the solution be after the addition of 10.0 mL of 0.010 M NaOH?
7
Acidic solutions have a hydronium concentration, [H3O+ ] that is which of the following?
> 10−7 M
What is a reversible reaction?
A reversible reaction is one that can proceed in either direction because reactants are not completely used to form products.
A student finds two unlabeled jars of white, solid substances. It is believed that one of the jars contains K2SO4 and the other BaSO4. What is a quick means of telling them apart?
Add water to each solid, K2SO4 is soluble and BaSO4 is insoluble
Which of the following ions could you separate, by causing them to precipitate, with the addition of HCl? (Hint: HCl is a source of chloride ions. Select all that apply.)
Ag+, Hg2+, Pb2+
Which of the following is NOT true about a net ionic equation?
All ionic species in the reaction mixture are shown.
Based upon your observations in Part A and logic, which ion(s) remaining in the supernatant from step 6 will precipitate when H2SO4 is added? (Select all that apply.)
Ba2+
This ion does not form a precipitate when HCl or ammonia is added. It will form a white precipitate in the presence of H2SO4.
Ba2+
Which ion(s) remain in the supernatant? (Select all that apply.)
Ba2+ Fe3+
none listed
Ba2+ and Fe3+
What is the chemical formula for calcium fluoride?
CaF2
Which ion emitted the lower frequency photons in the visible region: Ca2+ or K+?
Calcium ions emitted lower frequency photons than potassium ions since the calcium ions emitted light at a lower energy.
Which ion emitted the higher energy photons in the visible region: Cu2+ or Sr2+?
Copper(II) ions emitted higher energy photons than strontium ions since the copper(II) ions emitted light at a shorter wavelength.
Which element in the experiment has the most broad lines in its spectrum?
Cu (copper)
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-12 VE-8 SP-2
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-28 VE-14 SP-7
This ion does not precipitate with HCl but will form a precipitate when ammonia is added. The precipitate re-dissolves when acid is added and forms a red solution in the presence of NaSCN.
Fe3+
If there was a molecule with unequal Lewis resonance structures, which structure is the best according to the computer model?
For SCN−, a possible 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.
Choose the chemical in this experiment that has irritating vapors.
HCl
State a general rule concerning a system at equilibrium when more of one of the components is added.
If a component of the equilibrium reaction is added, the equilibrium will shift toward the opposite side of the reaction to consume the added material.
State a general rule concerning a system at equilibrium when one of the components is removed.
If a component of the equilibrium reaction is removed, the equilibrium will shift toward the same side of the reaction to replace the removed material.
How can you confirm that the resonance structures are equal for a molecule? Select the correct statement.
If the bond lengths are equal between pairs of atoms suspected of having resonance, then the molecule has equal Lewis resonance structures.
What is the effect of raising the temperature of a system at equilibrium?
It shifts the equilibrium toward the higher energy side of the equilibrium.
Which element in the experiment has the fewest intense red lines in its spectrum?
K (potassium)
Select the chemicals in this experiment that are listed as acidic or corrosive.
KMnO4, 3 M HCl
After the addition of H2SO4, the above sample is centrifuged and decanted. Which of the following cations remaining in the supernatant could you separate, by causing them to precipitate, with the addition of H2CO3? (Hint: H2CO3 is a source of HCO3− and carbonate ions. Select all that apply.)
Mg2+, Cu2+, Al3+, Fe3+
(c) Which chemical would one use in a cold pack? NH4NO3 CaCl2
NH4NO3
Choose the best explanation for the result you observed when NaNO3 was added.
Na+ and NO3− are not present in the equilibrium equation, and do not affect the concentration of FeSCN2+ which is responsible for the coloration.
During lab, you learned about exothermic and endothermic heats of solution. Which compounds below could be used for a cold pack? (Select all that apply.)
NaBrO3, KClO4
What is the chemical formula for sodium chloride?
NaCl
The buret in this titration experiment should contain which of the following?
NaOH solution
Based on these observations, can you make a generalization about the length of all single bonds compared to double bonds or all double bonds compared to triple bonds? What general rule can you make? Select the statement below that most closely agrees with your observations.
No conclusions can be made about the relationship between bond order and bond length for different pairs of elements. The differing sizes of the elements also impact the bond length.
Do your observations agree with what you have learned about formal charge? (See the table.)
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.
From the data collected and the information gained in lecture, would the anion have a dramatic effect on the color of the light emitted? Explain the observations you made during lab that support your answer.
No. The flame color did not vary with the anion. For example, the flame color was the same yellow-green color for barium chloride and barium nitrate.
Which ion emitted photons with the longer wavelength in the visible region: K+ or Na+?
Sodium ions emitted longer wavelength photons than potassium ions since the sodium ions emitted light at a lower frequency.
Which statements below describe the changes that molecules undergo when heat is applied during a phase change? (Select all that apply.)
The heat energy is used to move molecules further apart.The heat energy is used to overcome the intermolecular forces between molecules.
Considering the general rules you found for Group 1 cations and phosphate ion, which rule takes precedence?
The rule stating that compounds of Group 1A metals are generally soluble.
If one half the amount of AgNO3 was added to 100. g of water, what would happen to the temperature change?
The temperature change would be one-half as large
(a) What evidence indicates that a reaction has occurred? (Select all that apply.)
The temperature increased. A solid brown product formed.
Suppose the reaction equation were written as follows: 2 B(g) A(g) (c) Which of these statements would then be true? (Select all that apply.)
The ΔH value would have the same magnitude value but opposite sign., The K expression would be inverted.
What exceptions did you find to the Group 1 Rule?
There were no exceptions.
Which of the following is true about weak acids?
They have a small Ka and dissociate to only a small degree.
What should be done with the wastes in the Flame Test experiment?
They should be flushed down the sink with plenty of water.
Methyl Orange might be selected as an indicator for the titration of a weak base with a strong acid. Can you estimate the pH at the equivalence point?
Yes. The equivalence point should be somewhere between a pH of 3.1 and 4.4.
Conjugate acid-base pairs differ by which one of the following?
a proton
(b) for NH4NO3: In-Lab Question 2a. (i) The dissolution __________________ heat.In-Lab Question 2b. (ii) The process was ________________ In-Lab Question 2c. (iii) Based on this observation alone, the entropy ___________________
absorbed endothermic must have increased
Color in a substance arises from which two closely related processes?
absorption and emission
Select all of the following which might give off highly irritating vapors. (Select all that apply.)
acetic acid (HC2H3O2) ammonia (NH3) hydrochloric acid (HCl)
Select all of the following that are listed as corrosive. (Select all that apply.)
acetic acid (HC2H3O2) ammonia (NH3) hydrochloric acid (HCl) sodium hydroxide (NaOH)
What produces hydrogen gas in this experiment?
all reducing agents
Twisting the sleeve to open the holes (baffles) above the base of the burner does which of the following?
allows more air (oxygen) into the flame
In another laboratory, there are two solutions, one of which contains manganese(II) nitrate (Mn(NO3)2) and the other is 0.1 M potassium chlorate (KClO3). Some sodium sulfide (Na2S) is added to a sample of each. What happens next?
an MnS precipitate forms
If you condition the receiver beaker with the analyte solution prior to adding the measured volume of analyte to be titrated, what is the effect?
an increase in the volume of the titrant required to reach the end point an overestimation of the number of moles of analyte present
If you rinse your buret with deionized water, but do not condition with the titrant solution, what is the effect?
an increase in the volume of the titrant required to reach the end point an overestimation of the number of moles of analyte present
Face centered packing efficiency
best
Which two colors is green food coloring a mixture of? (Select all that apply.)
blue and yellow
__________________ cubic unit cells have identical particles on all corners, and in the center.(d) ________________cubic unit cells have identical particles on all corners, and on all faces of the cube.(e) ___________ cubic unit cells have identical particles on all corners of the cube.
body centered face centered simple
Based on your observations during the lab, which molecules below have a three dimensional structure? (Select all that apply.)
c2h6
Two gases, A and B, are at equilibrium in a sealed cylinder. Individually, gas A is colorless, while gas B is dark colored.The reaction might be written as: A(g) 2 B(g). (a) The cylinder should appear ______________ (b) When the system is cooled, the cylinder's appearance becomes very light colored. Therefore, the reaction must be _________________
colored endothermic
Based on your knowledge of trends in ionic radii, which spheres represent sodium ions and which represent chloride ions?
colorless = chloride ion, blue = sodium ion
Based on your knowledge of trends in ionic radii, which spheres represent cesium ions and which represent chloride ions? Remember that anions increase significantly in atomic radii and cations decrease in atomic radii.
colorless = chloride ion, green = cesium ion
Which spheres represent calcium ions and which represent fluoride ions?
colorless = fluoride ion, green = calcium ion
Sodium hydroxide (NaOH) is listed as which of the following?
corrosive
In-Lab Question 7b. When the volume increases, what is the effect on the pressure?In-Lab Question 7c. When the volume decreases, what is the effect on the pressure?In-Lab Question 7d. What type of relationship is this between variables?
decreases increases inversely proportional
The receiving beaker should contain which of the following at the beginning of the titration?
deionized water, phen, vinegar
What phrase best describes the lead wire?
dull gray and very bendable
(h) If ΔH is positive, the reaction is _______________ (i) If ΔH is greater than zero, and ΔS is less than zero, the process is always ________________ (j) If a process is spontaneous and endothermic, the change in ______________ must be positive.(k) In a nonspontaneous process, ___________ is the amount of energy that must be supplied to cause the process to occur.
endothermic nonspontaneous entropy free energy
For solution 5, the initial [NaOH] is ___________________ the final [OH− ], suggesting that NaOH is a _____________________ and that ______________
equal to strong base K>>1
For solution 1, the initial [HCl] is approximately _______________ the final [H3O+ ], suggesting that HCl is a ____________________ and that ____________
equal to strong acid K>>1
When working with a Bunsen burner, which of the following precautions must be observed? (Select all that apply.)
everything except "The burner must never be used in the presence of oxygen." and "The burner must never be used to heat metal."
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 > body-centered cubic > simple cubic
In Part B, a model of ____________, a mineral form of calcium fluoride, will be assembled.
flourite
ΔG is the symbol for ____________ (b) The amount of heat energy given off or absorbed by a process at constant pressure is the change in ____________(c) ______________ is related to the number of ways the energy of the system can be distributed.(d) In reaction energetics, the ______________ is the part of the universe being studied.(e) The part of the universe that interacts with a thermodynamic system is the _________________ (f) A reaction that gives off heat energy is ______________ (g) A reaction in which ΔG is negative is ________________
free energy enthalpy entropy system surroundings exothermic spontaneous
(a) for CaCl2: In-Lab Question 1a. (i) The dissolution _____________ heat.In-Lab Question 1b. (ii) The process was _______________ In-Lab Question 1c. (iii) Based on this observation alone, the entropy change ______________
gave off exothermic change cannot be determined
What was happening to the entropy of the system as the ice melted?
increasing a little
What was happening to the entropy of the system as the water heated?
increasing a little
What was happening to the entropy of the system as the water boiled?
increasing a lot
In general, are compounds containing carbonate (CO32− ) anion soluble or insoluble?
insoluble
In general, are compounds containing phosphate (PO43− ) anion soluble or insoluble?
insoluble
As the H3O+ decreases, what happens to the concentration of HBB, represented by the absorbance at ~470 nm?
it decreases
In the series from pH 6.3 to 6.8 to 7.3, the pH is increasing and the H3O+ is decreasing. As the H3O+ decreases, what happens to the concentration of BB−, represented by the absorbance at ~635 nm?
it increases
If HCl were added to a solution containing lead(II) ions, sodium ions, nickel(II) ions, and potassium ions, which ions would precipitate? (Select all that apply.)
lead ions
body centered cubic packing efficacy
medium
For solution 7, the initial [NH3] is ____________________ the equilibrium [OH− ], suggesting that NH3 is a _______________ and that ______________
much greater weak base K<<1
For solution 4, the initial [HC2H3O2] is ______________ the equilibrium [H3O+ ], suggesting that HC2H3O2 is a __________________ and that ___________
much greater than weak acid K<<1
When steam (water in the gas phase) condenses to liquid, ΔH of the system is __________, and ΔS of the system is _______________.
negative, negative
If you had started counting one mole of kernels when the earth was formed, would you be finished by now? (Hint: The age of the earth is about 4 billion (4 ✕ 109) years.)
no
Looking back at your data in Part A, are all single bonds the same length?
no
A solution contains Sc3+, Zn2+ and Au+. Some sodium sulfate (Na2SO4) is added to the solution. What happens next?
no precipitate
Based upon your Lewis structures for the postlab assignment, which molecules below have multiple Lewis resonance structures that are equal? (Select all that apply.)
no2-, so3
Which ion(s) remain in the supernatant from step 7? (Select all that apply.)
none
Phenolphthalein is listed as which of the following?
none listed
Cu and Mg2+
not react
At temperatures greater than 100°C, condensation is __________________ because the absolute value of the T·ΔS term in the Gibbs free energy equation is ______________ the absolute value of the ΔH.
not spontaneous greater than
In the flame test experiment, you will be working with two types of hazard. Which are they? (Select all that apply.)
open flame and hydrochloric acid, corrosive solution
Which absorbed color in Data Table C has the longest wavelength and lowest frequency?
orange
Based on your Lewis structures for the postlab assignment, which molecules below have a three dimensional structure? (Select all that apply.)
pcl3, ch2cl2
If a sodium hydroxide solution were added to a solution containing lead(II) ions, sodium ions, nickel(II) ions, and potassium ions, which ion(s) would remain in the supernatant? (Select all that apply.)
potassium and sodium ions
You have a solution suspected to contain copper(II) ions, barium ions, or iron ions. Which of the following solutions might be added to determine which cation is present?
potassium sulfate
CH3OH(aq) + Br−(aq) CH3Br(aq) + OH−(aq) ΔH = +78 kJ/mol. You must maximize the yield of the product. Which of the following actions should you take? (Select all that apply.) the equilibrium is _____________
remove CH3Br as it is formed, run the reaction with excess Br− ion, heat the reaction, run the reaction with excess CH3OH, less than one
A decreasing concentration of [H3O+] causes the equilibrium to shift to the ...
right, increasing the [BB−].
If one spills hydrochloric acid on one's hands, what is the FIRST thing one should do?
rinse them in running water
(a) Cations are __________ than the elements from which they form.(b) Anions are__________ than the elements from which they form.
smaller, larger
You are presented with a mixture of iron(III) ions, calcium ions, and lead(II) ions. Your goal is to separate and isolate the ions as three separate solids. What solutions might you add (and in what order) to accomplish this? (Hint: If adding a solution forms a precipitate with more than one of the ions present, it does NOT separate the ions.) ___________ solution, followed by _____________ solution, followed by _______________solution
sodium chloride, sodium sulfate, sodium hydroxide
AgClO4 soluble or insoluble
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?
soluble
In general, are compounds containing sulfate (SO42− ) anion soluble or insoluble?
soluble
Li3PO4 soluble or insoluble
soluble
LiOH soluble or insoluble
soluble
In Part A1, which oxidizing agents are to be reacted with KI (potassium iodide)?
the ones that did not react with H2O2
In Part A2, which reducing agents are to be reacted with 3 M HCl?
the ones that did not react with water
Based on the Lewis structure for C2H4, consider the following. (a) The electronic geometry about the carbon atom is (b) The orbital hybridization about the carbon atom is which of the following? (c) The molecular geometry about the carbon atom is
trigonal planar sp2 trigonal planar
Based on the Lewis structure for CH2O, consider the following. The electronic geometry about the carbon atom is The orbital hybridization about the carbon atom is which of the following? The molecular geometry about the carbon atom is
trigonal planar sp2 trigonal planar
The _________ is the smallest repeating three-dimensional array that includes the stoichiometry of the compound as given by its empirical or molecular formula.
unit cell
Which absorbed color in Data Table C has the shortest wavelength and greatest frequency?
violet
Which ion emits light of the highest energy?
violet
In what units will the cell potential be measured in?
volts
For this experiment, which gas property is the independent variable? Which gas property is your dependent variable?Which gas properties are unchanged?
volume pressure moles and temperature
When cleaning the wire between flame tests, most of the cleaning is accomplished when?
while rinsing the wire with acid
Which ion has the highest energy absorption maximum?
yellow-violet
H3C6H5O7 + 3 OH− → C6H5O73− + 3 H2O (a) What is the stoichiometry of H3C6H5O7 to OH−?
1:3
Use what you learned in lab about atoms in cubic structures to answer the following questions about a solid whose crystal structure was found to have atoms "A" in corner and center sites and "B" in the face sites of a cubic unit cell.How many "A"s are there in a unit cell?How many "B"s are there in a unit cell?
2 and 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-14 VE-8 SP-3
Calculate ER, VE, and SP for the formula CH4 (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-16 VE-8 SP-4
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)).
ER-20 VE-10 SP-5
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-20 VE-12 SP-4
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-24 VE-12 SP-6
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)).
ER-24 VE-16 SP-4
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)).
ER-24 VE-18 SP-3
After the addition of HCl, the above sample is centrifuged and decanted. Which of the following cations remaining in the supernatant could you separate, by causing them to precipitate, with the addition of H2SO4? (Hint: H2SO4 is a source of sulfate ions. Select all that apply.)
Sr2+, Ba2+
A student can get help with CH102..
at the Tutorial Center in FOX 152. by making an appointment to see his/her instructor. via the "Help Desk" or "Ask Your Teacher" feature in WebAssign.
The Mg2+/Mg couple was not tested when measuring half-cell potentials. Based on its behavior in Part A, where would you place it in the order you developed above?
at the top of list
When an ordered arrangement of particles extends over a long distance in a solid, the material is considered
crystalline
Why should silver nitrate be handled carefully? (Select all that apply.)
dark spots on skin
What happened to the pH when the 0.010 M NaOH was diluted to 0.0010 M NaOH?
decreased
Based on the Lewis structure for N2O, consider the following. The electronic geometry about the central nitrogen atom is The orbital hybridization about the central nitrogen atom is which of the following? The orbital hybridization about the central nitrogen atom is which of the following?
linear sp linear
Based on the Lewis structure for C2H2, consider the following. (a) The electronic geometry about the carbon atom is (b) The orbital hybridization about the carbon atom is which of the following? (c) The molecular geometry about the carbon atom is
linear sp linear
A general rule concerning temperature changes to equilibrium systems is that the input of energy (raising the temperature) shifts the equilibrium to the higher energy side of the equilibrium. Based on your observations, which side of the equilibrium is the higher energy side?
reactant side
Which ion emits light of greatest wavelength?
red
Because acid-base reactions are highly exothermic, which of the following should you NOT mix together?
solutions with concentrations greater than 0.1 M
What is the predicted hybridization at an atom which is surrounded by two double bonds? What is the predicted bond angle of this atom? What is the predicted shape of this atom?
sp 180 linear
What is the predicted hybridization at an atom which is surrounded by a double bond, a single bond, and a lone pair of electrons? What is the predicted bond angle of this atom? What is the predicted shape of this atom?
sp2 120 bent 120
If the pressure of steam is 1 atm and the temperature falls below 100°C, the condensation process is ___________, and ΔG is __________________-
spontaneous, negative
Based on the Lewis structure for C2H6, consider the following. (a) The electronic geometry about the carbon atom is (b) The orbital hybridization about the carbon atom is which of the following? (c) The molecular geometry about the carbon atom is
tetrahedral sp3 tetrahedral
Based on the Lewis structure for NH3, consider the following. (a) The electronic geometry about the nitrogen atom is (b) The orbital hybridization about the nitrogen atom is which of the following? (c) The molecular geometry about the nitrogen atom is
tetrahedral sp3 trigonal pyramidal
Based on the Lewis structure for H2O, consider the following. The electronic geometry about the oxygen atom is The orbital hybridization about the oxygen atom is which of the following? The molecular geometry about the oxygen atom is
tetrahedral sp3 bent 109
Based on the Lewis structure for CH4, consider the following. (a) The electronic geometry about the carbon atom is (b) The orbital hybridization about the carbon atom is which of the following? (c) The molecular geometry about the carbon atom is
tetrahedral sp3 tetrahedral
