At –80°C, K for the reaction N2O4(g) 2NO2(g) is 4.66 × 10–8. We introduce 0.049 mole of N2O4 into a 1.0-L vessel at –80°C and let equilibrium be established. The total pressure in the system at equilibrium will be: (0.78 atm)

In the first 12.0 s of the reaction, 1.6×10−2 mol of O2 is produced in a reaction vessel with a volume of 0.340 L . What is the average rate of the reaction over this time interval?

In the first 12.0 s of the reaction, 1.6×10−2 mol of O2 is produced in a reaction vessel with a volume of 0.340 L . What is the average rate of the reaction over this time interval?

The questions below refer to the following system: Co(H2O)6 2+ + 4 Cl– CoCl4 2– + 6H2O pink blue

When cobalt(II) chloride is added to pure water, the Co2+ ions hydrate.

The hydrated form then reacts with the Cl– ions to set up the equilibrium shown here. 27.) What change will the system undergo if hydrochloric acid is added? (It should become more blue and the equilibrium will shift to the right.)

A mixture containing 15.0 mol% hexane balance N2 flows through a pipe at 6.53 kmol/h. The pressure is 2.00 atm (abs) and the temperature is 100°C. If I want to begin to condense the hexane, what temperature do I need cool to? If I want to condense 80% of the hexane, what temperature do I need to cool to?

Show that the following are eigenfunctions of the Laplacian operator and determine the eigenvalues: a. (r^-1)sinkr

b.( r^-3)[(sin^2)θ]sin2φ

1.A sample of nitrogen at 20.0 °C has a volume of 954 mL at a pressure of 1,101 mmHg. To change the volume to 1,496 mL, what must be the new pressure?

2. A sample of nitrogen has a volume of 4.65 L at 1,639 mmHg and 51 °C. What volume will it occupy at standard temperature and pressure?

3. A sample of O₂ gas with a volume of 6.43 L was collected at 278 °C. What is the volume of the gas if the temperature is changed to 99 °C at constant pressure?

an unfortunate effect of drinking too much alcohol, known as a hangover, is attributable to the acetaldehyde formed when ethanol is oxidized. there is some evidence that vitamin b1 can cure a hangover. how can the vitamin do this? Can I see a mechanism

1. You work for a crafts supply company, KidKrafts, making calcium carbonate for their chalk products. They have recently decided to add plaster of Paris as one of their products. The key ingredient in plaster of Paris is calcium sulfate (CaSO4). You have been asked to adapt your knowledge of making calcium carbonate from calcium chloride dihydrate (CaCl 2 •2H2O ) and anhydrous sodium carbonate (Na2CO3) to making calcium sulfate. To make the most profit, you will be using the same stock of calcium chloride dihydrate as for the chalk. Therefore, you need to make sure that you use only the necessary amounts of each reactant. Your boss has asked you to not only figure out how to make the calcium sulfate but to prove that you don’t have any excess of either reactant.

a. The first step is figuring out what you need to mix together to make calcium sulfate. You know that the combination of calcium chloride and sodium carbonate worked well to make calcium carbonate in lab. Propose one chemical that you could react with calcium chloride to make calcium sulfate.Give two reasons why the chemical you chose will work. (Hint: What can you replace sodium carbonate with to make calcium sulfate instead of calcium carbonate?)

b. Now that you’ve selected a reactant, write out its (a) complete and (b) net ionic reaction with calcium chloride. You can ignore the waters of hydration on calcium chloride for this step.

c. If you run the reaction above using a solid mixture of exactly the right amount of each reactant, how can you prove that there is no excess? Describe the steps involved with this test. (Hint: Think about how you determined which reactant was in excess in the lab.)

d. Since you are developing a new procedure with a new chemical, you need to check how will you store it at the lab. Look up the MSDS of the reactant you proposed. What does your boss need to keep in mind when storing this chemical?

e. To try out your reaction and test for correct amount, you first need to determine how much of the reactants you need. What mass of your proposed reactant will you need to react with 1.000 g of calcium chloride dihydrate?

Materials:

Reaction Buffer 0.5 M Tris HCl pH 8.0 with 5 mM MgCl2

Alkaline phosphatase: 500 μg/mL stock solution in the buffer above. Keep enzyme on ice!

p-nitrophenyl phosphate: 1000 μM and 10000 μM stock solutions in reaction buffer

1) Using the enzyme stock solution above and the dilution equation, calculate the volumes needed to prepare 2 mL of three enzyme dilutions consisting of 100 μg/mL, 125 μg/mL, and 150 μg/mL. Use the reaction buffer to make these dilutions.

2) Calculate the amount of substrate needed for each of the following concentrations 10 μM, 25 μM, 50 μM, 100 μM, 200 μM, 500 μM, 1000 μM, and 2000 μM using the two stock solution concentrations listed above. Use the 1000 μM stock solution to calculate dilutions from 10-200 μM and the 10,000 μM stock solution to calculate from 500 μM-2000 μM. The final volume is 1.0 mL (or 1000 μL) for each dilution. Also calculate the volume of buffer needed, given that we will add 100 μL of the enzyme solution and the final volume is 1.0 mL (or 1000 μL) for each dilution.

What is the final pH at 25°C when 56 mL of 0.139 mol/L NaOH(aq) and 30 mL of 0.187 mol/L HA(aq) are mixed. Assume that HA is a weak monoprotic acid with pKa = 4.99 at 25°C

Part B

What is the pH after 0.150 mol of HCl is added to the buffer from Part A? Assume no volume change on the addition of the acid.

Express the pH numerically to three decimal places.

Part A What is the pH of a buffer prepared by adding 0.809 mol of the weak acid HA to 0.507 mol of NaA in 2.00 L of solution? The dissociation constant K a of HA is 5.66× 10 −7 . Express the pH numerically to three decimal places

A) Calculate the concentration of all species in a 0.490 M solution of H2SO3.

B) Calculate the concentration of all species in a 0.165 M solution of H2CO3.

Preparation of Ammine Complexes of Cobalt(III)

1) Give at least two differences between the two preparations that are carried out in this lab.

2) Base on the structures of complex ions shown in this lab, draw a pictures od what you think the complex ion [Fe(NH3)6]+2 would look like.

3) Suggest another small molecule that, like water and ammonia, might make a good ligand. Remember that ligands are electron pair donors, which means that one atom must have a lone pair of electrons on it. Draw the Lewis dot structure of the molecule you think would make a good ligand.

4) How would your percent yield be affected if you didn't dry your product completely? Explain your answer.

5) Why do you think both reaction mixtures were cooled before the products were collected by filtration?

6) What was the purpose of the hydrogen peroxide used in this lab?

7) What might have happened if the temperature of the oven were set to 210 Celsius instead of 110 Celsius called for in the procedure?

P23-27: Molar absorptivity data for the cobalt and nickel complexes with 2,3-
quinoxalinedithiol are εCo = 36,400 and εNi = 5520 at 510 nm and εCo = 1240 and εNi = 17,500 at 656 nm. A 0.425-g sample was dissolved and diluted to 50.0 mL. A 25.0-mL aliquot was treated to eliminate interferences; after addition of 2,3quinoxalinedithiol, the volume was adjusted to 50.0 mL. This solution had an absorbance of 0.446 at 510 nm and 0.326 at 656 nm in a 1.00-cm cell. Calculate the parts per million of cobalt and nickel in the sample.