lab report for separation and purification of benzoic acid, benzoin, 1,4-dibromobenzene

1. There is nothing like the smell of BBQ in the summertime. Many people use propane gas Barbeques to cook the perfect steak. Here is the reaction that is occurring while the steak sizzles on the grill:

C₃­H₈(g)   + O₂(g) --> CO₂(g) +   H₂O (g)

The balanced reaction has a DH^o_rxn = -2217 kJ. If a steak must absorb 7.2x10^-4 kJ to reach a perfect medium rare, and if only 15% of the heat produced by the barbeque is actually absorbed by the steak, what mass of H₂O is emitted into the atmosphere when this steak is cooked? (Hint: don’t forget to balance the reaction)

2. A student performed this lab with a marshmallow. He used 50.0 g of water and recorded a temperature of 21°C before heating and 30°C after heating. The marshmallow and fork weighed 21.5 g before heating and 21.1 g after heating. What was the total energy (in J) of the marshmallow? What was the energy per gram of the marshmallow?

The commercial concentrated hydrochloric acid is rated at 38 w/w%. The density of the solution is d = 1.18g.mL. Calculate the molarity of HCl (cHCl), molality of HCl (cR,HCl), and the mole fraction of HCl (xHCl).

If the observed rate law for a reaction is: rate = k(NO)(O₃), the reaction is

A. first-order overall

B. first-order in O₃

C. third-order overall

D. second-order in NO

(a) At what temperature do the Fahrenheit and Celsius scales have the same numerical value? (b) The Fahrenheit and Kelvin scales? (c) Describe the basis of each of these three temperature scales. The two cryogenic liquids I use in the lab are liquid nitrogen and liquid helium. What are the boiling points of those two liquids (e) in Fahrenheit? (f) in Kelvins?

Many years ago, I was obliged to polish to a mirror finish the leather shoes and belt of a certain sergeant to a mirror finish. The only way of achieving the desired result was to use copious quantities of spit, a trick which was taught to me by various people who had spent time in the army. My question is ... why does spit enhance the shine of shoe polish? And perhaps a related question ... modern shoes don't seem to require polishing. What surface finish is applied in the manufacturing process which gives an everlasting shine?

calculate the concentration of nickel (II) ion in the solution after the addition of 25.0 mL of 0.200 M NaCN to 60.0 mL of 0.0100 M Ni(NO3)2 (Kf is 2.0x10^31 for [Ni(CN)4]^2-)

Bragg's Equation Problem

X-rays of wavelength .0960nm are diffracted by a metallic crystal, angle of first order (n=1), is measured to be 17.8. What is the distance (in pm) between the layers of atoms responsible for diffraction?

I do this:

96pm / 2sin17.8 and I keep getting ~173.9pm

The answer is supposed to be 157pm. What am I doing wrong?

1. Why is the EDTA salt dried only at 80o C (i.e., why not 100o C)?

2. Suppose you did not heed our warnings and stored your EDTA solution in a conventional glass bottle (instead of a plastic bottle) -- how would this affect your final results (i.e., would they be high, low, or unchanged)? Explain.

3. Why is it not necessary that the plastic storage bottles be dry before transferring the EDTA for storage ?

4. Would the titration of Ca2+ with EDTA at a pH of 5 be feasible? Why or why not?

A gaseous mixture of CO and CO2 has a density of 0.9967 g/L at 14.24°C and 490.1 mm Hg. What is the mass percent of CO?

A solution is made by mixing 15.5 g of Sr(OH)2 and 40.0 mL of 0.230 M HNO3.

Part A: Write a balanced equation for the reaction that occurs between the solutes.

Part B: Calculate the concentration of OH− ion remaining in solution.

Part C: Calculate the concentration of Sr2+ ion remaining in solution.

Part D: Calculate the concentration of NO−3 ion remaining in solution.

Part E: Is the resultant solution acidic or basic?

1) a) write balanced molecular and net ionic equations for the neutrilization of NaOH by KHP( mol. WT= 204.23). Khp is an abbreviation for potassium hydrogen phthalate, KHC8H4O4,a subtance of known high purity with one acid hydrogen as indicated by the formula.

b) if 2.8 g of 204.23 KHP is dissolved in water and titrated with 40 ml of NaOH to the phenolphthalein endpoint, what is the molarity of the NaOH solution?

c) this now standardization solution of NaOH is used to find the molecular weight of an acid H2A which has two acid hydrogen. write a balanced molecular equation for this titration reaction.

d) if 1.08 g of this acid requires 37.18 of the NaOH solution for titration to the appropriate endpoint. calculate the molecular weight of the unknown acid H2A.

A researcher was attempting to quantify the amount of DDT (dichlorodiphenyltrichloroethane) in spinach with gas chromatography using a chloroform internal standard. To begin, the researcher examined a sample containing 6.00 mg/L DDT standard and 2.50 mg/L chloroform as the internal standard, producing peak areas of 5041 and 9537, respectively. Then, the researcher collected 10.85 g of spinach, homogenized the sample, and extracted the DDT using an established method (assume 100% extraction), producing a 3.32 mL volume of unknown sample. The researcher then prepared a sample that contained 1.00 mL of the unknown sample and 1.25 mL of 10.45 mg/L chloroform, which was diluted to a final volume of 25.00 mL. The sample was analyzed using GCMS, producing peak areas of 7671 and 11805 for the unknown and chloroform, respectively. Calculate the DDT concentration in the spinach sample. Express the final answer as milligrams DDT per gram of spinach.

1. a) Predict the behavior of all five compounds (biphenyl, benzophenone, ortho-dichlorobenzene, 1-naphthol, and benzhydrol (also called "benzohydrol") on both TLC (Thin Layer Chromatography) and GC-MS (Gas Chromatography-Mass Spectroscopy). Which one do you expect to have the largest Rf on the TLC? Which one will have the smallest Rf? Which will have the longest and shortest retention times on the GC?

1. b) Ortho-dichlorobenzene has a molecular weight of 147.00 g/mol, but its MS has a very small relative abundance of the 147 peak. Instead, it has peaks at 146 (100% relative abundance), 148 (65%), and 150 (10.6%). The peak at 147 is about 6.6% as big as the 146 peak. What causes this distinctive molecular ion region for this compound? What peaks (note the plural) would you expect to see on the mass spectrum for the fragment (note the lack of plural) caused by loss of one chlorine atom (one of the C-Cl bonds breaking) during the ionization process?

1. c) For the other four compounds, note which peak on the mass spectrum you expect to corresponds to the molecular ion for the molecule, and give the approximate M+1 abundance (relative to the molecular ion) expected based on the isotopic abundance the elements present. In addition, predict at least one major fragment which you would expect for each compound.

1. d) Based on your fragmentation analysis for the previous question, describe how you would expect to be able to tell these five compounds apart by their GC-MS even if you were unable to detect the molecular ion region (that is, if all three compounds fragmented 100% of the time).

Partial Pressure/Total Pressure Question

Consider the equation:

(CH3)2N2H2(l) + 2N2O4(l) ---> 3N2(g) + 4H2O(g) + 2CO2(g)

150.0g of (CH3)2N2H2(l) reacts with excess dinitrogen tetroxide and the product gases are collected at 127°C in an evacuated 250L tank. Assuming the reaction has a 100% yield and all gases behave as ideal gas.

A) How many moles of N2 could be produced after the reaction completed?

B) What is the partial pressure of nitrogen gas produced?

C) What is the total gas pressure in the tank after the reaction?