8. Here we are going to consider the differences between spectra and chromatograms. A list is given below of characteristics and behaviors of UV spectra and liquid chromatography. Some characteristics listed apply only to spectra. Other characteristics apply only to chromatography. And here’s the tricky bit, some characteristics apply to both. From the list below enter each characteristic that is correct for that instrumental plot on the line associated with that instrumental plot. Be careful, think about your choices, misplaced characteristics are negative points.

1. Usually has molar absorptivity values reported in homogeneous liquid solution

2. In our work in this lab, the solvent system is the eluent

3. Spans the UV and visible regions of the electromagnetic spectrum

4. Can be used for analytical work

5. Displays radiation absorption by molecules in solution

6. Displays the retention/separation by an appropriate stationary phase of molecules in solution

7. Provides information about how molecules are distributed between mobile and stationary phases

8. Can be used to identify unknown components in samples

9. Has time as the independent variable on the detector output plot

10. Has wavelength as the independent variable on the detector output plot

11. Has absorbance as the dependent variable on the output plot

12. Is concerned with electronic transitions in molecules

13. Is concerned with molecular distribution between phases

14. May show the instrument output plot at a constant flow rate

A. Liquid Chromatography plot characteristics are: _______________

B. UV spectral plot characteristics are: ________________

2. For the diprotic weak acid H2A, Ka1 = 2.7 × 10-6 and Ka2 = 8.8 × 10-9. What is the pH of a 0.0500 M solution of H2A? What are the equilibrium concentrations of H2A and A2– in this solution?

The Ka of a monoprotic weak acid is 7.84 × 10-3. What is the percent ionization of a 0.149 M solution of this acid?

At 1 atm, how much energy is required to heat 55.0 g of H2O(s) at –22.0 °C to H2O(g) at 151.0 °C? Enthalpy of fusion 333.6 J/g 6010. J/mol Enthalpy of vaporization 2257 J/g
40660 J/mol Specific heat of solid H₂O (ice)
2.087 J/(g·°C) *
37.60 J/(mol·°C) *  Specific heat of liquid H₂O (water)
4.184 J/(g·°C) *
75.37 J/(mol·°C) *  Specific heat of gaseous H₂O (steam)
2.000 J/(g·°C) * 36.03 J/(mol·°C) *

A 280.0 mL buffer solution is 0.270 M in acetic acid and 0.270 M in sodium acetate.

What is the initial pH of this solution? Express your answer using two decimal places.

What is the pH after addition of 0.0150 mol of HCl? Express your answer using two decimal places.

What is the pH after addition of 0.0150 mol of NaOH?Express your answer using two decimal places.

The good chemist is tasket with determining the concentration of manganese for a water sample drawn from a well next to a mine. To analyze the sample using absorbance spectroscopy, she prepares six sample (0-5) by adding 10.00 mL well water to 50.00-mL volumetric flasks, then adding increasing volumes of 25.00 ppm maganese solution, and diluting the resulting solution to 50.00 mL with 0.1 M HNO3. Final analysis at lambda(max)= 280 nm produced a graph of absorbance vs ppm Mn with best-fit line y = 0.0428x + 0.0487.

a) What is the concentration in ppm of manganese in the well water sample?

b) A field method of analysis was developed for testing soil near the mine where a .570 g sample of soil is quickly dissolved in acid with an oxidizing agent and diluted to 100 mL.

i) While you wait for the extraction, you calivrate your USB-spectrometer with a 3.15x10^-4 M standard of MnO4- with an average absorbance of .407 at 565 nm in a 1 cm cuvette. A blank solution made from DI water and acid had an absorbance of .078. Find the molar absorptivity of permanganate complex

ii) A few mL of the unknown solution is placed in a 1 cm cell and the transmission is found to be 30% at 565 nm. Calculate the concentration of manganese in the extracted sample.

iii)What was the weight percent of manganese in the original soil sample. iv) Explain in one sentence why permanganate appears to be a purple color

A. The freezing point of water H₂O is 0.00°C at 1 atmosphere.

How many grams of iron(II) nitrate (179.9 g/mol), must be dissolved in 228.0 grams of water to reduce the freezing point by 0.300°C ?

_____ g iron(II) nitrate.

B. The freezing point of water is 0.00°C at 1 atmosphere.

If 14.42 grams of ammonium acetate, (77.10 g/mol), are dissolved in 165.8 grams of water ...

The molality of the solution is _______ m.

The freezing point of the solution is _____°C.

Will leave a thumbs up!!!

Calculate the equilibrium constant for the reaction
S₂O₈^2-(aq) + 2 Fe²⁺(aq) --> 2 Fe³⁺(aq) + 2 SO₄^2-(aq) at 25.0°C, given that the standard cells potentials for the two half reactions at this temperature are
S₂O₈^2-(aq) + 2 e^- 2 SO₄^2-(aq) E = +2.08 V
Fe³⁺(aq) + e^- Fe²⁺(aq) E = +0.77 V

Increased gaseous CO2 concentrations are leading to decrease pH of ocean water which in turn causes harm to shellfish populations. Write all the appropriate equilibria (solubility and acid ionization) relevant to these phenomena. In complete sentences briefly, explain the phenomena using Le Chatliers Principle.

1. A sludge containing 4% solid (by weight) needs to be thickened by centrifugation to ≥15% solid for disposal. The centrifuge has a high constant speed and produces a dewatered sludge containing 20% solid. To increase the processing capacity while still meeting the disposal requirement, you decide to bypass (i.e., not dewater) some of the feed sludge and blend the untreated sludge with the dewatered (20% solid) sludge, so as to produce a final sludge with a 15% solid content. Assume all sludge streams have the density of water.

(a) Give the centrate production rate (in L/min) and the percent solid (of the total coming in) discharged via the centrate?

(b) What % of the feed sludge is bypassed (i.e., not centrifuged)?

2. Eutrophication is a natural aging process all lakes undergo as nutrients and organic matter accumulate from their drainage basins. Over time the accumulated nutrients enable increased aquatic growth and stimulate biological activities. The increase in phytoplankton causes the lake to become murky, while decaying organic matter depletes the available dissolved O2. Further accumulation of silt, nutrients, and organic matter causes the eutrophic ("well-fed") lake to become shallower and warmer with more plants growing in the shallow edges. This process transforms lakes into bogs and marshes over time. Natural eutrophication is usually quite slow, often measured in thousands of years before major changes occur. What human activity has done is rapidly accelerate this process (called "cultural eutrophication") by introducing large quantities of nutrients. Sources of nutrients include municipal wastewater, industrial wastes, and runoff from fertilized agricultural land. The introduction of superfluous nutrients disturbs the natural balance of the system, causing excessive algae growth and water quality deterioration. Algal blooms are the unsightly and often malodorous clumps of rotting debris along the shoreline and thick mats of dead organic matter in the lake. A nutrient of major importance that enter fresh water bodies such as lakes from the aforementioned sources is phosphorous. C = 20% C = 15% Q = 100 L/min C = 4% bypass centrifuge C = 0.1% ("centrate") 2 Consider a phosphorus-limited lake with a surface area equal to 8 x 107 m 2 that is being fed by a stream with a flow rate of 15 m3 /s and a phosphorus concentration of 0.01 mg/L. An outfall from a wastewater treatment plant also adds 1 g/s of phosphorus to the lake, but its volumetric flow rate is small and can be ignored. The outflow rate from the lake is the same as the inflow (15 m3 /s). Because phosphorus can attach to suspended particles in lake water, the phosphorus in the lake can also be removed through particle settling (to sediment), which occurs at a rate of 10 m/yr. For the questions below, assume the lake is a cylindrical CSTR.

(a) Draw a diagram to represent the processes involved in phosphorus mass balance. List all sources and sinks. Estimate the steady-state phosphorus concentration in the lake.

(b) An acceptable level of phosphorus in the lake is 0.01 mg/L, above which eutrophication is considered likely. By what percent must the wastewater treatment plant reduce its phosphorous discharge into the lake to achieve this concentration?

3. A textile finishing process involves drying fabric that has been treated with a volatile solvent. The drying process involves evaporation of solvent and removal of solvent vapor by air. The wet fabric entering the dryer contains 50% solvent by weight. Air enters the dryer at a rate of 8 kg per kg of solvent-free fabric. The drying process is 92% efficient; i.e., 92% of entering solvent is removed from fabric and carried out by air. What is the weight % of solvent in the dried fabric? What is the mole % of solvent vapor in the exhaust? The molecular weight of the solvent is 46 g/mol.(Note: Dried fabric still contains some solvent; i.e., dried fabric is not solvent-free).

4. A process heater burns 4.8 kg of natural gas per minute, and the air supply rate is 20% higher than the stoichiometric rate. Exhaust from the heater is sent to a heat exchanger, where water vapor is condensed and removed from the exhaust. Assume natural gas is all methane (CH4), air contains 21% O2 and 79% N2, and the combustion of CH4 is complete, what is the mole % of CO2 in the cooled exhaust?

Calculate the pH of a 0.449 M aqueous solution of acetylsalicylic acid (aspirin) (HC₉H₇O₄, K_a = 3.0×10^-4) and the equilibrium concentrations of the weak acid and its conjugate base.

1.) Please show all work

a.) Draw the reaction for imidazole, a weak base, ionizing water. You might need to look up the structure of imidazole and be careful about where you protonate or deprotonate it. Label all acids and bases and conjugate pairs.

b.) Find the pH of a strong base solution: 250 mM Mg(OH)2

c.) Find the pH of a weak base solution: 250 mM NH3 (Kb = 1.75 × 10–5)

For each of the following balanced chemical equations, calculate how many moles of product(s) would be produced if 0.640 mol of the first reactant were to react completely.

(a) BaCl₂(aq) + 2 AgNO₃(aq) → 2 AgCl(s) + Ba(NO₃)₂(aq)

(b) S(s) + 2 H₂SO₄(aq) → 3 SO₂(g) + 2 H₂O(l)

(c) C₃H₈(g) + 5 O₂(g) → 4 H₂O(l) + 3 CO₂(g)

(d) BaCl₂(aq) + H₂SO₄(aq) → BaSO₄(s) + 2 HCl(aq)

Consider the titration of 100.0 mL of 0.100 M NaOH with 1.00 M HBr. Find the pH at the following volumes of acid added.

Make a graph of pH versus V_a = 0, 1.0, 5.0, 9.0, 9.9, 10.0, 10.1, and 12.0 mL.

When 200. mL of 0.40 M hydrochloric acid solution is mixed with 3.76 g of aluminum metal, how many moles of hydrogen gas would be produced?

6HCl(aq) + 2Al(s) → 2AlCl3(aq) + 3H2(g)