Chemistry Questions and Answers May 07, 2020

Which of the following statements about energy dagrams and reactions are true a) A onestep reaction will have two energy maxima between reactants and products on its reaction coordinate diagram. b) One part of a reaction mechanism would be the understanding of which bonds break and form during a reaction.

1. Use the periodic table to determine the element corresponding to each of the following electron configurations. a. [Ar]4s23d1 Express your answer as a chemical symbol. b. [Kr]5s2 Express your answer as a chemical symbol. 2. Arrange the following elements in order of decreasing atomic radius: Ba, Sb, Cl, Pb, and Se. Rank elements from largest to

Draw energy level diagram of CuSO4.5H2O and of [Cu(NH3)4]SO4.H2O

2. Calculate the NBOD, CBOD, and THOD of a waste containing 100 mgL NH3N and 100 mgL isopropanol (C3HOH) and 100 mgl of methylamine (CH3NH2). Hint C3H,OH O2 CO2 H20

If the acetamide (H 2 N-CNH-CH 3 ), in Step 1 was replaced by urea (H 2 N-CO-NH 2 ), what would the product of Step 1 be? provide the mechanism by using curly arrows .

heat EtO OEt EtO H2N CH3 Step 1 H CH3

1. An FM station broadcasts music at 93.5 MHz (megahertz, or 106 Hz). Find the wavelength (in m, nm, and ) of these waves. 2. x-ray has a wavelength of 1.3 . Calculate the energy (in J) of one photon of this radiation. (1 A = 1X10-10m) 3. Use the Rydberg equation to find the wavelength (in nm) of the photon emitted when an electron in an H atom

Using nitroxidemediated polymerization, propose a synthetic route for the amphiphilic block copolymer poly(acrylic acid)b(polystyrene). Provide suggested reaction conditions (solvents, temperature, etc.) and draw explicit structures for all reagents used in your synthesis approach. Show the mechanism for each step (either within your scheme or

Please identify the chemical compound (name) according to these IR spectra. Please also include an explanation with the peaks frequency. the sharpest peak on the left is at 3000. This graph starts right to left 100-4000.

1320 60 1190 66 Z9 74 3632 79 546 66 2044 70 2787 BL 2299 2248 3548 19 2749 1075 1006 3249 BOR2 2907 10 2962 19 2401 34 74 Z190 64 2624 169 2521 84 1464 14 836 84 2451 86 1432 23 785 49 2460 86 1107 69 767 77

Energy and Specific Heat Are you completing this experiment online? Yes Specific Heat of an Unknown Metal Identification number of unknown metal 4 Mass of unknown metal (g) 18.07 Mass of calorimeter cup (g) 1.79 Masses and Temperatures for Two Trials Trial 1 Trial 2 Mass of calorimeter and water (g) 47.26 47.90 Temperature of boiling water bath

For the following reaction: Draw the linear regioisomer for the reaction above. What controls regioselectivity? Why does the diastereocontrol vary when preparing all four stereoisomers?

Ph OH OCOMe cat. cat. Et Zn, L1 LC(COD)2, L2 THF, RT Ac OH Ph

A chemical analysis of dissolved organic carbon (DOC) in a water sample yields the following Water Analysis Carbon (wt. ) 44.23 Oxygen (wt. ) 47.79 Hydrogen (wt. ) 3.81 Nitrogen (wt. 5) 3.11 Sulfur (wt. ) 0.59 Molecular weight (Dalton) 3814 (a) Derive the empirical (simplest) formula for the DOC. (b) Calculate the atomic HC and OC ratios (c) Is

Interpret the structure of the hypothetical compound, MxJy, in terms of lattice points occupied by the ions, coordination number, and coordination environment. The structure is shown at right, gray spheres are M ions and green spheres are Jion. Describe how the stoichiometry is determined.

There is a sample of fish oil that contains 4% of a free fatty acid, 80% of a diglyceride formed by two units of the same fatty acid not yet identified and 16% of unsaponifiable matter. Knowing that the saponification index of the sample is 102.267 mg NaOH / gram oil, deduce and represent the structure of the fatty acid involved Data: Palmitoleic

O EPA (C205w3) ODHA (C226 w3) O Acido linoleico (C182) O Acido palmitoleico (C161) O Acido palmtico (C160)

23. Provide an acceptable synthesis for the following. Make sure you show all intermediates

A 250.0mL sample of 0.4375M aniline, C 6H5NH2 (Kb= 3.8x 10-10) reacted with 2.250L of gaseous hydrocyanic acid, HCN (Ka= 6.2x 10-10) at 25.0C and 8353.0 mmHg. Assuming the volume of the solution did not change, calculate the pH and concentrations of all species present at equilibrium. (Hint: remember that when you add equations together, you must

3. Consider the Pourbaix diagram of copper a. Identify the immunity, passivation, and corrosion areas of Cu in the Pourbaix diagram. 1.6 1.2 C 0.8 Cu(OH),(s) 0.4 Cu,0(s) Cuo 0.4 Cu(s) 0.8 1.2 8. 12 16 pH b. (TF). The transformation of Cu2 to Cuz0 is both potentialdependent and pH dependent. (TF). The transformation of Cu(OH)2 to Cu02 is both

Modify the given molecules so that they show the form that is dominant at physiological pH. cadaverine octopamine Select Draw Rings More Erase Select Draw Rings More Erase N H N H H, H N C N H H O CH, H. HC CH II HC CH 0 H

Calculate the value of CP at 298 K and 1 atm pressure predicted for CH4(g) and C2H4(g) by the classical equipartition theorem. Compare the predicted results with the experimental results and calculate the percent of the measured value that arises from vibrational motions. Calculate the value of CP at 298 K and 1 atm pressure predicted for CH4(g)

9.86. You make some iced tea bydropping 164 g of ice into 500.0 mL of warm tea in an insulated pitcher. If the tea is initially at 20C and the ice cubes are initially a OC, how many grams of ice will still be present when the contents of the pitcher reach a final temperature The tea is mostly water, so assume that it has the same density (1.0gmL),

From the corresponding Henrys law coefficient kx 8.64 104 bar, estimate the molarity of N2 (gas) in water at 298 K when the water is in equilibrium with air at a total pressure of 1.06 bar . Assume that the ai is 78 N2 by volume (i.e., by mole number), and that the dissolved N2 does not affect the volume of solution. There are 55.3 moles of

The Henrys law coefficient of CO2 in water at 298 K is 1.6 103 bar. Calculate the molarity of CO2 in water at 298 K when the solution is in equilibrium with the atmosphere, which has an average CO2 abundance (by mole) of 3.94 104 and a pressure of 0.91 bar. There are 55.3 moles of water in L at 298 K. Express your answer using two significant

We have used Raoults law to obtain the expression for the freezing point shift of a solution RTXB Afus HAm If the activity of the solvent is given instead by aa k XA and the vapor pressures of the pure solvent and solute are P and P, what is the new equation for AT in terms of the mole fraction of solute 21n kA O AT RT Afus HAm RT2(In kA XB) Afus

Indicate whether the following parameters will increase (), decrease () or remain unchanged (0) during the process described. Drag the appropriate labels to their respective targets. Reset Help parameter process , , or 0 S adiabatic expansion T adiabatic expansion T increasing P AvapHm increasing P PB increasing Xg in a solution

11. Identify the following drugs and provide an explanation for their mechanism of action. HN HDHC

Atomic emission spectroscopy and the method of standard addition are used to determine the Na concentration and its uncertainty in an unknown sample. Increasing amounts of a 1.75 ugmL standard Na solution are added to a series of volumetric flasks containing 10.00 mL of the unknown solution. The volumetric flasks are then diluted to a final volume

Complete the following sentences about oxaloacetate. Match the words in the left column to the appropriate blanks in the sentences on the right. ResetHelp The ion Ag+ would be reversible The ion {m Ag^+} would be a reversible blank inhibitor because the structure of {m Ag^+} is blank to the structure of any organic compound a13. inhibitor because

Use a spreadsheet and construct curves for the following titrations. Calculate potentials after the addition of 10.00, 25.00, 49.00, 49.90, 50.00, 50.10, 51.00, and 60.00 mL of the reagent. Where necessary, assume that [H+] ? = 1.00 throughout.

4 C 50.00 mL of 0.02600 M Fe (CN)6 with 0.01300 M T1. Potential after the addition of 10.00 mL of the reagent Potential after the addition of 25.00 mL of the reagent Potential after the addition of 49.00 mL of the reagent Potential after the addition of 49.90 mL of the reagent Potential after the addition of 50.00 mL of the reagent Potential

Suppose that 5.00 mL of blood serum containing an unknown concentration of potassium, [K+]i, gave an atomic emission signal of 3.00 mV. After the addition of 1.00 mL of 30.0 mM K + and dilution of the mixture to 10.00 mL, the emission signal increased to 4.00 mY. (a) Find the concentration of added standard, [S]r. in the mixture. (b) The initial

1a. Add to this drawing the substrate molecule binding to the active site and be specific about the shape of the substrate molecule. Next to your drawing write the chemical properties of the substrate that are important for it to bind to the enzyme. 1b. If the amino acid serine present in the active site were to be mutated to valine, how will this

Using cyclohexanone, 2nitrobenzaldehyde and acetophenone, show how you would synthesize the depicted tetracyclic product. Give reagents and conditions and product for each step in your synthesis. NO

9.Consider the reaction 3NO2(g)+H2O=2HNO3(aq)+NO(g) where Delta H=-137 kJ.How many kilojoules are released when 92.3g of NO2 reacts?

In a binary mixture, the density of ethanol is 0.7880 g cm -3 at 20.0 0 C. Its equilibrium vapor pressure at 20.0 0 C is 40.0 torr. Calculate the change in its chemical potential at this temperature and composition, if its pressure is changed from 40.0 torr to 1 atm. (Hint: recall u j = G j,m ).

Of the following four elements which pair has atoms closest in size Na, K, Mg Ca O Na Mg O Mg Ca O K Mg O Na Ca

During gravimetric analysis of copper, which of the following are considered to be true Select all that apply. It is a quantitative chemical analysis The desired constituent in a known mass of the sample is separated Acetone must be used in the filtration process The excess aluminum foil must be destroyed

A buffer solution contains 0.350 M hydrofluoric acid and 0.390 M sodium fluoride . If 0.0353 moles of nitric acid are added to 250 mL of this buffer, what is the pH of the resulting solution ? (Assume that the volume does not change upon adding nitric acid ) pH = ?

Methyl methacrylate (MW = 100 g/mol, 1.5 M in benzene) is polymerized using AIBN (0.02 M in benzene) as an initiator at 85 C. The initial observed rate of polymerization at steady state is 1.5 x 10-5 M.s-1 . The thermal initiation of AIBN under similar conditions proceeds to afford active radical species with a measured fkd of 1.9 x 10-6 What is

Please fill in the table based on the given MS spectrum.

MS Data Molecular Formula IHD M (mz) Base Peak (mz) Lost Fragments Other Peaks (mz),Mass Spectrum Neutral Solid Unknown Relative Intensity 100 80 80 40 20 25 50 75 mz 100 125 M 138

1 In this experiment we tested for the ammonium ion using a fresh sample of the unknown. Why was this done, rather than using the solution left after a later step in the analysis Hhe

3. In the calculations it was assumed that a. Before any acetic acid was added, essentially all the indicator was in the In form. b. After the HCl was added, essentially all the indicator was in the Hin form. Justify these assumptions using the measured pH of these solutions and your experimental value for pK, to determine a. The fraction of the

Which of the following series correctly lists the salts in terms of increasing lattice energy OA. Mgo Cao Sro B. LICI NacI NaF OC RDCI SRC2

Write a net ionic equation to show why the solubility of Pb(OH)2(s) increases in the presence of a strong acid and calculate the equilibrium constant for the reaction of this sparingly soluble salt with acid. Be sure to specify states such as (aq) or (s). K

Calculate the solubility of Ag,CO3 (a) in pure water and (b) in a solution in which CO, 0.203 M. 3D Solubility in pure water M Solubility in 0.203 M Co,2 M 3

If 12.0 ml. of 8.30104M Ba(CH3CO0), are added to 15.0 mL. of 1.10105 M (NH4)2Co, will solid BaCO3 (Kp 8.1x10) precipitate If a precipitate will not form, what carbonate ion concentration will cause a precipitate of barium carbonate to form If a precipitate will form, what is the minimum Co, that could have been present without initiating

a) List all four protecting groups on this molecule, and what functional group they are protecting. b) When subjected to hydrogenation over Pd/C catalyst, which two protecting groups are removed? c) The next step in this synthesis is an intramolecular amide bond formation between the two unprotected groups. Using this fact combined with your

NHBoc N NH H IZ HN Cbz IZ Ph COMe COBn

Show that each ring of thiamine 1 fulfills the requirements for aromaticity. n

ci NH2 CH3 H3C CH2CH,OH

What are the spectator ions present when aqueous solutions of titanium(IlI) acetate and sodium chromate are mixed Include charges, and use superscripts andor subscripts if necessary (click on the three dots on the top right hand of your answer box, next click the down arrow next to the B, I, U button.

a) Treatment of compound D with 1-hexylamine resulted in the exclusive displacement of the chloro group at position 7 to give the product E. Explain why reaction did not also occur at position 3 to displace the Bromo group in an analogous process. b) Three of the four nitrogens atoms of E are basic but the fourth is not protonated, even under very

NH2 heat D. Br E Br

If the acetamide (H 2 N-CNH-CH 3 ), in Step 1 was replaced by urea (H 2 N-CO-NH 2 ), what would the product of Step 1 be? (2 marks)

EIO DE heat NH HN CH Step I CH, POC, heat Siep 2 NH, EIO Step 3 HBr CHS NH Step 4 Br Her AgCI CH, Step 5 CH,CH,OH CH,CH,OH

a) Outline a mechanism for Step 2. (5 marks) b) Account for the selectivity seen in the electrophilic aromatic substitution reaction that has occurred in Step 3. Give a brief mechanistic justification of your answer. (5 marks) n

.CI NH3 H20 CI Step 1 N. NH2 2,3dichloropyrazine Br Step 2 H heat in ethanol (solvent) CI Br2 acetic acid (solvent) Step 3 E Br

Using the 1 cm path length and absorptivity coefficient calculated for question 1, and the data for Dilution sample #1, perform the following calculations. Note 1cm path length is being used because it is the standard size cuvette used in a laboratory spectrophotometer. a. Calculate the theoretical absorbance for Dilution 1: b. The phone is

a) Under conditions A, the doubly-deuterated product 15 is formed. Draw a mechanism to explain this outcome. b) Under conditions B, the mono-methylated product 16 is formed. Draw a mechanism to explain this outcome. What does the position of methylation tell you? c) Under conditions C, the decomposition product 17 is formed. Draw a mechanism to

Oz. Ar A N 1.2x CHLI, 78 c Ph. .D i. DO 15 Os Ar B Os5Ar .N. 1.2x CHLI, 78 c . 1x CHJ . HO (workup) .N. N Ph. Ph. 14 16 D 1.2XCHLI, 25 C i. D0 Ph. 17

A solution of sulfuric acid contains 28.99 by mass of H,SO, and has a density of 1.21 gmL. What is the molarity of H,SO, in this solution

a) Why is it difficult to diprotonate a diazine? (1 mark) b) Which is the only chlorodiazine that does not undergo easy nucleophilic substitution of the chloro group, and why? (2 mark)

N. pyridazine pyrimidine pyrazine

Outline a reasonable mechanism for step 1 of the sequence.

ELONA NC. CO,Et NH NC EIOH NH. EIO HN Me 0C Me step 1 step 2 POCI, heat NH2 NH3 NC. NC. MeOH, 100 C Me Me step 3

2,4-Dibromothiazole 8 is a key intermediate in the synthesis of antifungal agents such as the melithiazoles. a) Compound 8 cannot be prepared by the bromination of the parent thiazole ring system. By consideration of the intermediates involved rationalize why the 5- position is the site of the first bromination. (3 marks) b) Fortunately compound 8

S La heat H2N NH2 ENH with aq. HCI Br, N excess POBr 98 yield Br 85 yield 8

a) Is the ylide N (phosphorane) shown above a stabilized or non-stabilized ylide? Explain your answer. (2 marks) n b) Redraw the structures below in your answer book and use them to draw Newman projections to show the likely approach of the ylide N to the aldehyde M. Ensure that you label any steric clashes or dipole moments that are of

PhP OEt OEt (0) (M) (N)

Give the major product of the following reactions with the appropriate stereochemistry and regiochemistry m. CH3 1. Hg(OAc)2, CH3 H3C 2. NaBH4 n. CH3 PdC, D2 H3C CH3 1. CpRu(CH3CN)PF6, SiH(OEt) o. Ph 2. KF 3 dil. HCI

0TICI4 1. H3C TiCl4 H3C H. H. 2. OCOH HCI OH a Proton transfer d Electrophilic addition g SN1 Nucleophilic substitution b Lewis acidbase e El Elimination h SN2 Nucleophilic substitution c Radical chain substitution f E2 Elimination Identify the mechanism by which each of the reactions above proceeds from among the mechanisms listed. Use

Determine the (a) order, (b) rate constant, (c) starting concentration, (d) halflife and shelf life of the reaction from the concentration data given below. time hour mcgml 0 0.25 0.5 1 2 3 4 7 8 9 10 100 100 100 88.24969 7.407407 77.88008 3.846154 99.5 60.65307 1.960784 99 36.78794 0.990099 98.5 22.31302 0.662252 98 13.53353 0.497512 97.5 8.2085

2.20 mol of Ng at 120 C and 6.45 bar undergoes a transformation to the state described by 335 Cand 1.9s bar. Part A Calculate AS it K 30.81 11.87 x 102.3968 x 10 1.0176 10 Express your answer with the appropriate units. J AS 48.86 K

1. Suppose that a of NyO4 (9) and 0500 mol of NO (q and the equilibrium Ng Oq Cg) 2NO2(g is aftained at 25c and2atm. Find the eguilibrium compostice 2. True or false system initially contains 0300md 298 is zeno for O b) ApH for Qg) for O d) The reacion NgG) 3H(g) 2NH3 (9) is zero t is zero 400 3. Find K at 60OK for N49) 2N(g) for 49) 2N using

100.-mL sample of 0.100 M solution of Ca2+ ions is being complexometrically titrated with 0.100 M EDTA. pH of the solution is being maintained at 9.0 by a buffer. Acidity constants of EDTA are: Ka1 = 1.010^-2, Ka2 = 2.210^-3, Ka1 = 6.910^-7, Ka2 = 5.510^-11 Formation constants of the Ca-EDTA complex is Kf = 5.0110^10 Relevant textbook example: 9.3

The value of K, is 2.55 x 106 for a weak monoprotic acid whose initial concentration is 0.244 M. What is the pH of this acid solution

Consider the following reaction where K, 1.29x10 at 600 K COCI, (2) Co (g) Cl, (g) A reaction mixture was found to contain 0.129 moles of COCI, (g), 5.08x10 moles of CO (g), and 4.47x10 moles of Cl, (g), in a 1.00 liter container. Indicate True C) or False (D for cach of the following 1. In order to reach equilibrium COCI,(g) must be consumed.

1) Consider barium sulfate crystals in saturated aqueous solution with interfacial energy of 120 mJm and Gibbs free energy barrier of 5.02x1019 J a. Show with calculations whether a nucleus with a radius of 0.8 nm would grow or dissolve back into the solution. b. Determine whether the energy barrier to the nucleation process is greater for a cube

A 0.100 M KCI solution is placed in contact with a 0.100 M LICI solution. Which statements are TRUE for the junction between the two solutions The mobilities of the ions are K 7.62 x 108 m(sV), Li 4.01 x 108 m(sV), and Cr7.91 x 10 m(sV). I The KCl side of the junction will be positive as K diffuses more quickly across the junction than CIr. IL

A vibrational mode at 655.0 cm1 is used in quantitative Raman measurements. The Raman instrument can be equipped with a 785 nm diode laser source or 1064 nm NdYAG laser source. Assume the sources operate at the same radiant power. What would be the relative intensity of the Stokes Raman signal obtained using the diode laser to the Stokes Raman

For the following equation: Br 2 (l) + 2KI (aq) I 2 (s) + 2KBr(aq) Identify the half reactions and use them to determine if the reaction is spontaneous

Synthesize the following molecule using any reagents you desire. Ph HO.

Br ,, at TsO NaSH DMSO NaOH Br DMSO NaCN Br KOCH, La CH,CN

2. Direct titration 10.00 0.02 mL of an unknown KHP solution required 11.54 0.02 mL of 0.1010 0.0006 M NaOH to reach the end point. a. What is the concentration of KHP in the unknown solution reported with uncertainty 0.040 0.1166 b. If the unknown solution was prepared by dissolving 5.128 g of the unknown KHP (204.22 gmol) in 100.00 ml of

aa. 1. Hg(OAc)2, H2NCH,Ph 2. NaBH4 CH3 bb. HSO4, H2O H,SO4 . 1. NaNH2 2. CH3CH2I 3. Na, NH3

Using the standard reduction potentials here, calculate the standard potential for the following cell in V (make sure you dont round your answer) Culs)Cu2(aq)Mn2(aq),H(aq)Mn02(s)Pt(s) Your Answer

What change will be caused by the addition of a small amount of HCI to a solution containing fluoride ions and hydrogen fluoride Assume volume remains constant. Select one a. The concentration of fluoride ions will increase and the concentration of hydrogen fluoride will decrease. b. The fluoride ions will precipitate out of the solution as its

Muriatic acid, an industrial grade of concentrated HCl, is used to clean masonry and cement. Its concentration is 11.7 M . For routine use, a diluted solution of 3.50 M is prepared. How many milliliters of 3.50 M muriatic acid solution contain 29.6 g of HCl?

i. In step (a), the hydrazone 8 reacts with 2 equivalents of butyl lithium (BuLi) to generate the anion 14. Propose a mechanism for this conversion. (4 marks) ii. Identify and name the type(s) of selectivity occurring in step (b). (2 marks) iii. Step (d) is accomplished using carbonyl diimidizole 15. Outline a mechanism for this transformation. (3

TBSO OBn OTPS OBn OTBS TPSO a. nBuLi, THE NNHSO2A. H 10 8 TBSO TBSO TBSO OTPS OTPS PS c. LIAIH4, Et,0 OBn OBn OBn d. H. to to 11 13 12 TPS tertbutyldiphenylsilyl (Si((C6H5)2C(CH3)3)) TBS tertbutyldimethylsilyl (Si((CH3)2C(CH3)3)) Bn benzyl (CH2PH) acac acetylacetonato (CH3COCH2COCH3) BuLi butyl lithium (CH3CH2CH2CH2LI) b. .....

Tosyl hydrazones adjacent to epoxides can undergo the Eschenmoser Fragmentation, like this reaction of 16 to give the unsaturated carbonyl compound 17. The mechanism of this reaction is closely related to the Shapiro reaction. i. Redraw compound 16 in your answer book and indicate clearly which bonds will be broken in step (e). (2 marks) ii. Apply

Ts NEN N . Ts H. 16 17 O00

List the properties that are needed for a molecule to be aromatic. Consider the following ring systems. Comment briefly about each and indicate clearly (with reasons) whether or not it should be aromatic? (7 marks)

N N. CH3 N. CIO, ZI ZI

Pyrrole is much more acidic than diisopropylamine. Explain.

pka 16 pKa 3D pka 36 ZI Z

Rationalise the following observation using valence-bond structures for the possible intermediates. Pyrrole undergoes electrophilic substitution easily and predominantly in the 2- position. (6 marks)

E Z Z

The pyridine N-oxide, compound A, is a new drug claimed to be useful for the treatment of senile dementia. Industrial synthesis of it is outlined below. i) Suggest a mechanism to account for Step 1 in the sequence. ii) Suggest a mechanism to account for Step 2 in the sequence. iii) Suggest a mechanism to account for Step 4 in the sequence. iv) The

CI CN CN CN POCI3 OEt heat H2N Step 1 Step 2 oxidant Step 3 S. S. CI CN CN H Step 4 Compound A ZI

A synthesis of the broadspectrum antibiotic, metronidazole, is outlined below: i) Suggest a mechanism to account for Step 1 in the sequence. (3 marks) ii) Suggest a mechanism to account for Step 3 in the sequence. In your answer explain the reason for the regioselectivity of this transformation. (4 marks)

2 equivalents heat in acetic acid NH3 H. H3C H. Step 1 NH H3 1. conc. HNO3 conc. H2SO4 Step 2 2. neutralisation NO2 NO2 ZON N. NH HN N. N. Step 3 CH3 CH3 CH3 2methyl4(5)nitroimidazole metronidazole