Quant Final

A solution with 0.0837 M X and 0.0500 M S' gave areas Ax=423 and As'=372. Then 10.0 mL of 0.050 M S' plus 10.0 mL of unknown were diluted to 25.0 mL. The chromatogram gave Ax=553 and As'=286. Find [X] in the unknown. a. [X]= 0.050 M b. [X]= 0.156 M c. [X]= 0.233 M d. [X]= 0.142 M

[X]= 0.142 M

Ascorbic acid (vitamim C) in a 50.0 mL sample of orange juice was analyzed by an electrochemical method that gave m=a detector current of 1.78 µA. A standard addition of 0.400 mL of 0.279 M ascorbic acid increased the current to 2.50 µA. Find the concentration of ascorbic acid in the orange juice. a. [X]= 4.98 mM b. [X]= 5.37 mM c. [X]= 6.22 mM d. [X]= 5.73 mM

[X]= 5.37 mM

A 0.0251g sample of impure piperazine contained 71.29 wt% piperazine How many grams of product will be formed if this sample is analyzed by the following reaction: Piperazine (FM: 86.136) + Acetic Acid (FM: 60.052) -> Piperazine diacetate (FM: 206.240) a. .0428 g Piperazine diacetate b. .0655 g Piperazine diacetate c. .0468 g Piperazine diacetate d. .0341 g Piperazine diacetate

a .0428 g Piperazine diacetate

The first excited state of Ca is reached by absorption of 422.7 nm light. (a) What is the energy difference (J) between the ground and excited states? (b) The degeneracies are 𝑔∗/𝑔0= 3 for Ca. Find 𝑁∗/𝑁0 at 2500 K (c) By what percentage will the fraction in (b) be changed by a 15-K rise in temperature? (d) Find 𝑁∗/𝑁0 at 6000 K.

a) 4.699E-19 J b) 3.67E-6 c) 8.4% increase d) 1.03E-2

The acid HA has pka of 7. What is the quotient [A-]/[HA] at pH 6? a. 0.1 b. 0.2 c. 2.0 d. 1.0

a. 0.1

A solution containing 2.24 ppm PbCrO4 exhibits 80.0% T in a 1 cm cell at 550 nm. Calculate the molar absorptivity of PbCrO4 at this wavelength. Molar mass of PbCrO4 is 323.19 g/mol. (L/cm mol) a. 1.40E4 b. 1.27E3 c. 2.80E-3 d. 2.24E4

a. 1.40E4

A solution containing 4.48 ppm KMnO4 exhibits 85.9 %T in a 1 cm cell at 520 nm. Calculate the molar absorptivity of KMnO4 at the wavelength. (L/cm mol) a. 2.3E3 b. 4.2E4 c. 2.6E3 d. 3.3E4

a. 2.3E3

An atomic absorption analysis is to be done on the calcium in a sample of powdered milk. A 12.55 gram sample of the powder is wet ashed in nitric acid and diluted to 50.00 mL with distilled water. A 1.00 mL aliquot of this is transferred to a 50.00 mL solution using EDTA. Using a wavelength of 422.6 nm in an atomic absorption experiment, this diluted sample showed an absorbance of 0.375. A standard calcium sample (treated the same way) with a known concentration of 10.0 ppm provided an absorbance of 0.759. What is the ppm of calcium in the powdered milk? a. 247 ppm b. 437 ppm c. 4.94 ppm d. .0759 ppm

a. 247 ppm

The first excited state of Ca is reached by absorption of 422.7 nm light. If the energy difference between the ground and excited state is 4.699E-19J and the degeneracies are 𝑔∗/𝑔0= 3 for Ca, find 𝑁∗/𝑁0 at 2500 K. a. 3.67E-6 b. 1.03E-2 c. 3.67E-8 d. 7.41E4

a. 3.67E-6

The base association constant of phosphate are kb1= 0.024 kb2=1.58E-7 kb3= 1.41E-12. Calculate ka2 a. 6.33E-8 b. 7.09E-3 c. 4.2E-13 d. 1.58E-8

a. 6.33E-8

Increasing the number of observations (measurements) in an experiment will: a Reduce the size of the confidence interval b. Increase the size of the confidence interval c. Reduce the precision of the experiment d. None of the above

a. Reduce the size of the confidence interval

In homogeneous precipitation: a. When precipitation is slow, particle growth dominate over nucleation to give larger, purer particles b. When precipitation is slow, nucleation dominates over particle growth to give larger, purer particles c. When precipitation is rapid, crystallization dominates over nucleation to give smaller particles d. When precipitation is rapid, nucleation domination over crystallization to give larder, purer particles

a. When precipitation is slow, particle growth dominates over nucleation to give larger, purer particles.

Atomic emission is more sensitive to flame instability that atomic absorption because: a. in atomic emission spectroscopy, the analytical signal is produced by the relatively small number of excited atoms or ions b in atomic absorption the signal results from absorption by the much smaller number of unexcited species c. changes in flame conditions dramatically influences the number of unexcited species d. changes in flame conditions have a much smaller effect on the number of excited species

a. in atomic emission spectroscopy, the analytical signal is produced by the relatively small number of excited atoms or ions

Which is not a characteristic of ICP that makes it suitable for atomic emission spectroscopy? a. the low and varied electron concentration which leads to fewer ionization interferences b. the atoms and ions formed are formed in a nearly chemically inert environment c. sample residence times are long so that desolvation and vaporization are essentially complete d. the temperatures are high which favors the formation of atoms and ions

a. the low and varied electron concentration which leads to fewer ionization interferences

Express absorbance, A=0.0356, in terms of transmittance a. 92.10 b. .9210 c. 90.12 d. .9012

b. .9210

Calculate the pH of a 1.00 L solution of 0.100 M NH3 after the addition of 0.01 mol NH4Cl for NH3, pkb=4.74 a. 11.56 b. 10.26 c. 8,26 d. 9.26

b. 10.26

A researcher has collected the following sample. data. The mean of the sample is 5. Calculate the standard deviation: 3,5,12,3,2 a. 8.944 b. 4062 c. 13.2 d. 16.5

b. 4.062

Calculate the pH of a solution that is 0.04 M in NaH2PO4 with: ka1 (H3PO4)= 7.11E-3 ka2 (H3PO4)= 6.32E-8 a. 4.37 b. 4.71 c. 5.02 d. 2.36

b. 4.71

Red light with a wavelength of 633 nm strikes a grating at normal incidence (θ = 0). The grating spacing is d = 1.6 µm. At what angle is n = +2 diffracted beam expected? a. .79 b. 52 c. .52 d. 79

b. 52

The energy difference is 2.107 eV. Calculate the wavelength of radiation that would be absorbed in excited the electron. (1 eV =1.6E-19J) a. 529 nm b. 590 nm c. 576 nm d. 609 nm

b. 590 nm

A 25.0 mL sample of 0.150 M hypochlorous acid is titrated with a 0.150 M NaOH solution. What is the pH after 13.3 mL of base is added? The ka of the hypochlorous acid is 3.0E-8 a. 4.43 b. 7.58 c. 7.46 d. 7.25 e. 1.34

b. 7.58

A gathering agent is: a. A precipitate used to prevent impurities from reacting with the precipitant b. A precipitate used to collect a trace component c. Used to allow a precipitate to stand in contact with the mother liquor and promote recrystallization d. None of the above

b. A precipitate used to collect a trace component

What statement about buffers is true? a. Buffers consist of a strong acid and its conjugate base b. Buffers resist change in pH upon addition of small amounts of strong acid or strong base c. Buffers have pH of 7 d. A buffer does not change pH on addition of a strong acid or strong base

b. Buffers resist change in pH upon addition of small amounts of strong acid or strong base

Identify the conjugate acid of SO42- a. H2SO4 b. HSO4- c. H2SO3 d. H3O+ e. SO32-

b. HSO4-

When analyzing a sample set,what would be true if the sample number was increased? a. increasing the number of samples would increase the accuracy b. increasing the number of sample would decrease the standard deviation c. increasing the number of samples would increase the standard deviation d. increasing the number of samples increases the mean

b. increasing the number of samples would decrease the standard deviation

At equilibrium, : a. the rate constants of the forward and reverse reactions are equal b. the rates of the forward and reverse reactions are equal c. all chemical reactions have ceased d. the value of the equilibrium constant is 1 e. the limiting reagent has been consumed

b. the rates of the forward and reverse reactions are equal

The results of five determinations were found as follows: Trial 1= 1.3% Trial 2= 1.2% Trial 3= 1.0% Trial 4= 0.98% Trial 5= 1.4% If s=0.18, What is the confidence interval(at 95% level) that can be reported for the trials: a. 1.4 +/- 0.22 b. 1.2 +/- 0.32 c. 1.2 +/- 0.22 d. 1.4 +/- 0.32

c. 1.2 +/- 0.22

For the same data of problem-5, the "range" is: a. 1 b. 2 c. 10 d. 12

c. 10

The pH of a 0.55 M aqueous solution of hypbromous acid, HBrO, at 25C is 4.48. What is the ka? a. 3.3E-5 b. 3.0E4 c. 2.0E-9 d. 1.1E-9 e. 6.0E-5

c. 2E-9

What is the buffer range (for an effective 2.0 pH unit) for a benzoic acid/sodium benzoare buffer? ka for benzoic acid is 6.3e-5 a. 8.8-10.8 b. 7.4-9.4 c. 3.2-5.2 d. 4.7-6.7 e. 5.3-7.3

c. 3.2-5.2

Find Stand Deviation of the Following Data with a mean of 171: 166, 170, 172, 175 a. 4.1 b. 3.4 c. 3.8 d. 1.3

c. 3.8

A 25.0 mL sample of 0.723 M HClO4 is titrated with a 0.27 M KOH solution. The H3O+ concentration after the addition of 80.0 mL of KOH is _____M? a. 0.7 b. 0.4 c. 3E-13 d. 4E-2 e. 1E-7

c. 3E-13

What is the wavelength (angstroms) of a photon that has an energy of 4.38E-18 J? a. 2.3E7 b. 1.45E-16 c. 454 d. 6.69E15 e. 1.31E-9

c. 454 angstroms

Calculate the pH of a solution that is 0.04 M in NaHS with: ka1 (H2S)= 9.6E-8 ka2 (H2S)= 1.3E-14 a. 4.60 b. 8.39 c. 9.80 d. 4.71

c. 9.80

A solution containing which one of the following pairs of substances will be a buffer? a. RbCl, HCl b. KBr, HBr c. CsF, HF d. NaI, HI

c. CsF, HF

The "range" is the: a. Sum of the measured values divided by the number of measurements b. The standard deviation divided by the average c. Difference between the highest and lowest values d. Smooth bell-shaped curve superimposed on a set of data

c. Difference between the highest and lowest values

In Standard Deviation,s: a. Less scatter gives a higher standard deviation b. Less scatter gives a smaller standard deviation c. There's an inverse proportionality between scatter and standard deviation d. None of the above

c. Less scatter gives a smaller standard deviation

Choose the correct statement: a. The detection limit is not the same as the lower limit of detection b. The detection limit is the highest quantity of analyte that is significantly similar to the blank c. The minimum detectable concentration = 3s/m where "s" is the standard deviation of a low-concentration sample and "m is the slope of the calibration curve

c. The minimum detectable concentration = 3s/m where "s" is the standard deviation of the low-concentration sample and "m is the slope of the calibration curve

In a chromatography experiment, a solution containing 0.0837M X and 0.0666M S gave areas Ax=423 and As=347. To analyze the unknown, 10.0 mL of 0.146M S were added to 10.0 mL of unknown, and the mixture was diluted to 25.0 mL in a volumetric flask. This mixture gave the chromatogram with peak areas Ax=553 and As=582. Find [X] in the unknown. a. [X]= 0.173 M b. [X]= 0.131 M c. [X]= 0.143 M d. [X]= 0.138 M

c. [X]= 0.143 M

For the following reaction: 2C02 -> 2CO +02 H=-514 kj Le Chatelier's principle predicts that the equilibrium partial pressure of CO can be maximized by carrying out the reaction: a. at high temp and high pressure b. at high temp and low pressure c. at low temp and low pressure d. at low temp and high pressure

c. at low temp and low pressure

The output of a ruby laser at 700 nm when it is passing through a piece of quartz that has a refractive index of 1.65 is: a. 436 nm b. 448 nm c. 300 nm d. 424 nm

d 424 nm

How many photons are contained in a burst of yellow light (589 nm) from a sodium lamp that contains 623 kJ of energy? a. 2.48E25 b. 2.10E13 c. 3.06E30 d. 1.85E24 e. 4.03E28

d. 1.85E24

Calculate the pH of a solution that is 0.04 M in H3PO5 with ka1 (H3PO4)= 7.11E-3 a. 2.03 b. 1.37 c. 1.43 d. 1.86

d. 1.86

Ascorbic acid (vitamim C) in a 50.0 mL sample of orange juice was analyzed by an electrochemical method that gave m=a detector current of 1.78 µA. A standard addition of 0.400 mL of 0.279 M ascorbic acid increased the current to 3.35 µA. Find the concentration of ascorbic acid in the orange juice. a. 5.37 mM b. 3.16 mM c. 2.54 mM d 2.49 mM

d. 2.49 mM

Calculate the frequency in Hertz of an X-ray beam with wavelength of 1.0 Å. a. .03 Hz b. 3E5 Hz c. 3E10 Hz d. 3E18 Hz

d. 3E18 Hz

What is the pH of a buffer solution that is 0.172 M in hypochlorous acid and 0.131 M in sodium hypochlorite? The ka of the hypochlorous acid is 3.80E-8 a. 7.54 b. 14.12 c. 6.70 d. 7.30 e. 9.07

d. 7.30

What is the pH at the equivalence point of a weak acid-strong base titration if the 25 mL of aqueous hydrofluoric acid requires 30 mL of 0.4 M NaOH? ka (HF) = 6.76E-4 a. 5.75 b. 12.26 c. 1.74 d. 8.25

d. 8.25

In gravimetric analysis: a. A sample is burned in excess oxygen and the products are measured b. The mass of the analyte is used to calculate the quantity of the product c. An analyte is combusted and products measured using mass spectrometry and thermal conductance d. The mass of a product is used to calculate the quantity of the original analyte

d. The mass of a product is used to calculate the quantity of the original analyte

The advantage of a double beam spectrophotometer over a single beam is: a. low cost and simplicity in design b. the ability to analyze more than two samples at the same time c. increasing fluctuations in source intensity due to drift in electronic circuits d. the ability to irradiate the sample and solution simultaneously or nearly so

d. the ability to irradiate the sample and solution simultaneously or nearly so

Calculate the hydronium ion concentration in an aqueous solution with a pH of 9.85 at 25C. a. 8.70E-10 M b. 7.10E-5 M c. 6.50E-5 M d. 4.20E-10 M e. 1.40E-10 M

e. 1.40E-10 M

The pH of a solution prepared by mixing 45.0 mL of 0.183 M KOH and 35.0 mL of 0.145 M HCl is: a. 0.00824 b. 1.403 c. 12.923 d. 1.314 e. 12.597

e. 12.597

An aqueous solution contains 0.50 M NaOH at 25C. The pH of the solution is: a. 7.00 b. 13.50 c. 0.50 d. 0.301 e. 13.70

e. 13.70

What is the pH of an aqueous solution at 25C that contains 1.35E-8 M hydroxide ion? a. 7.87 b. 7.00 c. 8.00 d. 1.35 e. 6.13

e. 6.13

Determine the [H3O⁺] in a 0.265 M HClO solution. The Ka of HClO is 2.9E-8. a. 4.90E-4 M b. 1.10E-10 M c. 7.70E-9 M d. 1.30E-6 M e. 8.80E-5 M

e. 8.80E-5 M

Which of the following is the weakest acid? a. HF (ka=6.8E-4) b. Acetic acid (ka=1.8E-5) c. HNO2 (ka=4.5E-4) d. HClO (ka=3.0E-8) e. HCN (ka=4.9E-10)

e. HCN (ka=4.9E-10)

Amine bases are known as strong bases. (T/F)

False

One analysis with 4 samples found the standard deviation to be 3.8. Another analysis with 5 samples found the standard deviation to be 12. Use the F-test and determine if the two standard deviation are significantly different (at the 95% confidence level).

Fcalc=9.97 Ftable=9.12 ; Not statistically similar

Using the Grubbs test, decide whether the value 0.195 should be rejected from the set of results: 0.217, 0.224, 0.195, 0.221, 0.221, 0.223

Gcal=2.06 Gtable=1.822; 0.195 should be rejected

In the following set of measurements, the last result may be an outlier. Apply the Q-test (90% confidence level) to determine whether or not there is a statistical basis to reject the result: 2.7, 3.0, 2.6, 2.8, 3.2

Qcal=0.33 Qtable=0.64 @ 90% confidence; Keep the result

Brontsted and Lowry suggested that bases be defined as proton acceptors. (T/F)

True

HNO3 is a stong acid. (T/F)

True

Calculate the wavenumber (cm^-1) and energy (J/photon and Kj/mole of photons) of light with a wavelength of 2.50 µm.

Wavenumber: 4.0 cm^-1 J/photon: 7.95E-20 kJ/mol of photon: 47.9