ALLIED CHEM EXIT EXAM

A 0.5843 g sample of a plant food preparation was analyzed for its N content using Kjeldahl method, the liberated NH3 was collected in 50.00 mL 0.1062 M HCI. The excess acid required an 11.89 mL of 0.0925 M NaOH for back titration. Express the results if this analysis in terms %(NH4)2SO4.

47.61

A 0.917-g sample of canned tuna was analyzed by the modified Kjeldahl method. A volume of 20.59 mL of 0.1249 M HCI was required to titrate the liberated ammonia. Calculate the percentage of nitrogen in the sample.

3.93

A fluoride ion-selective electrode is used in two solutions. Both solutions have [F] of 5.00 x 10-3 M, but one has a pH of 2.00 and the other a pH of 7.00. You would expect that:

the potential would be lower in the pH 2.00 solution.

Branch of electrochemistry concerned with the relationship between the potential of an electrochemical cell and the concentration of the contents of the cell.

Potentiometry

It is a half-cell having a known electrode potential that remains constant at constant temperature and is independent of the composition of the analyte solution

Reference electrode

To find the concentration of manganese ions in a sample, the absorbance of different solutions containing known concentrations of manganese ions was also measured. The results are shown in the graph below. The absorbance reading for a 10 mL sample of manganese ions of unknown concentration is 0.18. Determine the amount (in mg) of manganese ions in the 10 mL sample.

4.38 mg

A solution contains 0.100 M sodium nitrate (NaNO3) and 0.200 M MgCl2. Find the ionic strength of the solution.

0.700 M

In the formula for determining the ionic strength, what does Z stand for?

charge

Which of the following equations represents a charge balance equation for a saturated solution of Ag₃AsO₄?

[Ag⁺] + [H⁺] = 3[AsO₄^3-] + 2[HAsO₄^2-] + [H2AsO₄^-] + [OH^-]

A 4.957 g sample of a hydrocarbon is burned in an excess of dioxygen, producing 9.284 g CO2 and water. What mass of hydrogen is contained in the original sample?

2.423 g

Analysis of a compound showed that it contained 76.0 % fluorine atoms and 24.0 % carbon atoms by mass. What is its empirical formula?

CF₂

A 3.903 g sample of a hydrocarbon is burned in an excess of dioxygen, producing 7.31177 g CO2 and 4.488 g H2O. What is the empirical formula of the hydrocarbon?

CH₃

Which substance would produce 2 mol of particles per mole of solute when dissolved in water?

NH₄CH₃COO

Which of the following electrochemical methods requires the formation of an insoluble form of the analyte?

electrogravimetry

In the cell notation: Zn(s) I Zn+2 (aq) II Cu+2 (aq) I Cu (s), which species acts as the oxidizing agent?

Cu⁺² (aq)

The limiting current in a linear sweep voltammogram is related to ____

The concentration of the analyte of interest

Predict the product for the following reaction.

IV

Provide the product for the following reaction sequence.

II

What is the IUPAC name for the following compound?

4,4-dimethylcycloheptanone

Which one of the following pairs of compounds will yield the following product in presence of sulfuric acid?

III

Provide the reagents necessary to carry out the following conversion.

NH2NH2/KOH, D

What is the IUPAC name for the following compound?

7-methyl-4-octanone

Predict the product for the following reaction.

II

In infrared spectroscopy, this is also known as the frequency accuracy advantage since the instrument is capable of self-calibration.

Connes

Blue light in the visible region has a longer wavelength than ____.

X-rays

Determine the statement that is not true regarding infrared spectroscopy.

Fingerprint regions are normally used to identify the functional groups present in a substance.

What is the IUPAC name for the following compound?

3-ethyl-3-pentanol

Predict the product for the following reaction.

III

Predict the product(s) for the following reaction.

II

Predict the major product for the following reaction.

III

Predict the product(s) for the following reaction sequence.

1,4-heptanediol

What is the IUPAC name for the following compound?

(1S,2S)-1,2-cyclopentanediol

Provide the reagents necessary to carry out the following conversion.

CrO₃/H₂SO₄/H₂O

A zinc-copper voltaic cell is represented as follows:

Zn(s) | Zn2+(1.0 M) | | Cu2+(1.0 M) | Cu(s)

Which of the following statements is false?

The copper electrode is the anode.

Calculate the mass of copper metal in grams produced at the cathode during the passage of 2.50 amperes of current through a solution of copper(II) sulfate for 50.0 minutes.

Do not include units in the answer box.

2.47

Consider the following reduction potentials:

Cd2+(aq) + 2e-Cd(s); E° = -0.40 V

Pb2+(aq) + 2e- Pb(s); E° =- 0.13 V

Cu2+(aq) + 2e Cu(s); E° = 0.34 V

Br2(l) + 2e-2Br (aq); E° = 1.07 V

Under standard-state conditions, which of the following reactions is spontaneous?

Cu²⁺(aq) + Cd(s) - Cu(s) + Cd²⁺(aq)

An oxidation occurs at the ____ of a Galvanic cell.

anode

What mass in grams of NaC₂H₃O₂ must be dissolved with 500 mL of 0.100 M acetic acid to make a 2L of buffer solution of pH=5? K_A=1.8 x 10-5

7.38

When preparing a buffer solution for a biological experiment, one should choose ____.

all of the aboveD

When the concentration of the acid and conjugate base components of a buffer are present in exactly equimolar proportions

the pH of the buffer solution is equal to the pKa of the acid component of the buffer

In the titration of a weak base with a strong acid, the pH before the equivalence point is ____.

greater than 7

At what volume of the titrant (in ml) will be used in the titration of 50.0 ml of 0.100 M acetic acid with 0.100 M NaOH so that the pH will just be equal to pKa of the acid? Ka = 1.75 x 10-5

25.0

Phenolphthalein is an acid-base indicator that is colorless in its acid form and pink in its basic form, changing at pH = 8.5. Bromcresol green is yellow in its acidic form and blue in its basic form, changing at pH = 4.8. A solution is colorless in phenolphthalein and blue in bromocresol green. Therefore we can conclude that the pH of the solution is ____.

between 4.8 and 8.5

The pH transition range of phenolphthalein is 8.2 - 10. What is the estimated pKa of this acid-base indicator?

9.1

Which of the following indicator(s) would be most suitable for the titration of acetic acid

(pKa = 4.74) with NaOH?

phenolphthalein (transition range pH 8.3 to 11)

A buffer solution is 0.500 M in acetic acid and 0.500 M in sodium acetate. Its pH is 4.74. What is its pH after dilution by a factor of 2?

4.74

Precipitates used in the gravimetric determination of uranium include Na₂U₂O₇(634.0 g/mol), (UO₂)₂P₂O-(714.0 g/mol), and V₂O₅.2UO₃ (753.9 g/mol). Which of these weighing forms provides the greatest mass of precipitate from a given quantity of Uranium?

V₂O₅-2UO₃

What do you call a co-precipitated impurity in which the interfering ion occupies a lattice site in the precipitate?

inclusion

The following pairs are metallic ions and their corresponding precipitating agent for gravimetric analysis except ____

Mg⁺² and H₂S

A compound is found to contain 27.3 grams of carbon, 4.55 grams of hydrogen and 36.4 grams of oxygen. The molecular weight is found to be 90.0. What is its molecular formula?

C₃H₆O₃

For the following reaction, which reactant functions as an acid?

II

For the following reaction, which reactant functions as a base?

II

A 2.4414-gram sample containing KCI, K₂SO₄ and inert materials was dissolved in sufficient water to give 250.0 mL of solution. A Mohr titration of a 50.00 mL aliquot required 41.36 mL of 0.05818 M AgNO₃. A second 50.00 mL aliquot was treated with 40.00 mL of 0.1083M of NaB(C₆H₅)₄. The reaction is: NaB(C₆H₅) + K+® KB(C₆H₅)_4(s) + Na⁺. The solid was filtered, reddisolved in acetone, and titrated with 49.98 mL of AgNO₃ solution according to the reaction: KB(C₆H₅) + Ag+ ® AgB(C₆H₅)_4(s) + K⁺

Calculate the percentage K₂SO₄ of the sample.

8.95

Calculate the molar concentration of dilute HCI solution if the of 0.2459 g of primary standard Na2CO3 required 36.52 mL of the acid (products are NaCl, CO2 and H2O)

0.1271M

Reagents that underwent superficial purification and are seldom used in analytical work.

technical reagents

Rank the following carboxylic acid derivatives in decreasing order (most to least) of reactivity towards nucleophilic substitution.

IV>I>III>II

Predict the product for the following reaction sequence.

2,2-dimethyl-1-propanol

What is the IUPAC name for the following compound?

formyl formate

What is the IUPAC name for the following compound?

3-methylhexanoic acid

Predict the product for the following reaction.

I

Which one of the following is the weakest acid?

4-hydroxybenzoic acid

Which of the following statements is/are incorrect?

i. In addition polymerization, monomers are merely added to form a chain and no other products are formed besides the polymer.

ii. In condensation polymerization, small molecules react with each other to form larger structural units while releasing smaller molecules as a byproduct.

iii. Monomers are the building blocks of polymers.

iv. Examples of biopolymers are carbohydrates and proteins.

None of the above

Which of the following base pairs is possible in RNA?

None of the above

What do you call a natural polymer made up of 2 up to 50 amino acids?

Peptide

Name the following:

3-methyl-1-pentyne

What is the common name for the following compound?

diphenylamine

What is the IUPAC name for the following compound?

N-butyl-2-pentanamine

Which of the following compounds is the strongest base?

IV

Which of the following compounds is least soluble in water?

III

Predict the major product for the following reaction.

IV

Predict the product(s) for the following reaction.

I

In the double indicator method, which of the following cannot form a compatible mixture?

NaHCO3 and NaOH

A series of solutions containing NaOH, Na2CO3 and NaHCO3, alone or in compatible combinations, were titrated with 0.1202 M HCI. Given are the volumes of acid required to titrate 25.00 mL portions of each solution each to a (1) phenolphthalein and (2) bromocresol green endpoint. Which of the following contains NaOH?

B

A 350 mg soda ash sample required 25.60 mL of 0.035 M HCI to reach the phenolphthalein endpoint and additional 34.80 mL to reach the methyl orange endpoint. Calculate the %composition of the soda ash.

7.7% NaHCO3 and 27% Na2CO3

A molecule which has absorbed a photon of energy in the visible range could move from the excited electronic state S1 to a highly excited vibrational level of the ground state (So) with the same energy. This process is:

Internal conversion

Transmittance is given as T = P/Po. If Po is the power incident on the sample, what does P represent?

Radiant power transmitted by the sample

In which of the following ways, absorption is related to transmittance?

Absorption is the negative logarithm of transmittance

Identify the choice that DOES NOT describe an internal standard.

exhibits zero signal when measured in the instrument

Which of the following is not true regarding emission spectra?

Emission spectra are normally measured at a detector positioned at 90° to the incident light.

Which one of the following compound is aromatic?

I

Which one of the following compound is aromatic?

III

Predict the major product for the following reaction.

II

Which one of the following compound is aromatic?

IV

Provide the reagent(s) that are necessary to carry out the following conversion.

t-butylbenzene 3434® 4-chloro-1-t-butylbenzene

Cl2, FeCl3

Predict the structure of the product for the following reaction.

I

Calculate the mass deficiency in g/mol of Zinc-64 (actual mass = 63.9291 amu).

Do not include units in the answer box.

0.6002

Which of the following statements concerning nuclear bombardment and transmutation is/are correct?

3 only

A nuclear ______ is a self-sustaining series of nuclear fissions caused by the absorption of neutrons released from previous nuclear fissions.

chain reaction

Which of the following statements concerning radioactive decay is/are correct?

1 and 2

What is the standard enthalpy change for the combustion of liquid cyclopentane, C5H10?

2C5H10(I) + 1502(g) - 10CO2(g) + 10H2O(I)

-6581.8 kJ

Reformulated gasolines

contain oxygenated compounds.

Which petroleum fractions can be used to make diesel fuel?

kerosene and fuel oil

Distillation separates components of a mixture due to differences in

boiling points

What is the IUPAC name for the following compound?

1-ethyl-2-methyloxirane

Predict the product(s) for the following reaction.

III

What is the IUPAC name for CH₃CH₂CH₂CH₂OCH₂CH₃?

1-ethoxybutane

Predict the product for the following reaction.

(Z)-3-hexene + mCPBA

I

Which of the following crown ether solvates lithium ions?

12-crown-4

What is the correct IUPAC name for the following compound?

12-crown-4

Which of the following equations represents a charge balance equation for a saturated solution of Ag₃ASO₄?

[Ag⁺]+ [H⁺] = 3[AsO₄^3-] + 2[HASO₄^2-] + [H2AsO4^-]+[OH^-]