Remarkably, a catalytic system that uses light energy to hydrolyze water into hydrogen H2(g)and O(g) has been devised (Science 334, 2011: 645-648) to capture and efficiently store solar energy. Hydrogen is "clean burning" in that it yields only H2O. In this problem you will contrast the combustion of 1 kgH2(g) to that of 1 kg of n-octane.

a. Calculate the enthalpy change on burning 1 kg of H2(g) to H2O(l) at 25∘C and 1 bar

b. Calculate the entropy change on burning 1 kg of H2(g) to H2O(l) at 25∘C and 1 bar.

c. Calculate the free-energy change on burning 1 kg of H2(g) to H2O(l) at 25∘C and 1 bar.

d. Calculate the enthalpy change on burning 1 kg of n-octane(g)to H2O(l) and CO2(g) at 25∘C and 1 bar.

e. Calculate the entropy change on burning 1 kg of n-octane(g)to H2O(l) and CO2(g) at 25∘C and 1 bar.

f. Calculate the free-energy change on burning 1 kg of n-octane(g) to H2O(l) and CO2(g) at 25∘C and 1 bar.

1.

a) Calculate the solubility of Pb3(PO4)2 in water.

b) Calculate the solubility of Hg2Br2 in water and in 0.300 M CaBr2. Explain why the solubilities are different in water and in 0.300 M CaBr2.

An unknown compound contains only carbon, hydrogen, and oxygen. Combustion analysis of a 1.893 gram sample of the compound produced 5.545 grams of carbon dioxide and 1.388 grams of water. The 1.893-gram sample contained 7.002 x 10-3 moles. What is the molecular formula for this compound?

Trying this one again too... it's a completely different question, I need to know how to make the (100 ml) solution.

Glacial acetic acid is 99.5% acetic acid (f.w. 60.052) by weight and has a density of 1.05g/mL.

Describe the operations needed to prepare exactly 100 ml of 0.100M pH 5.000 buffer, using the dry salt sodium acetate and the liquid glacial acetic acid.

If 10 mL of 0.025 M benzoic acid (K_a = 6.5 * 10^-5) is titrated with 0.01 M NaOH, what is pH after 0 ml, 20 ml, 50 ml, and 90 ml of base have been added?

Questions for Crystal Violet Lab.

1. Give the derivation of a first order rate equation and show why the plots of Ln ([dye]_o/[dye]_t) vs t should be linear.

2. What property other than [dye]_t and [dye]_o could have been used for the plot of Ln ([dye]_o/[dye]_t) vs t? Explain your answer.

Determine the pH during the titration of 33.7 mL of 0.345 M triethylamine ((C₂H₅)₃N, K_b = 5.2×10^-4) by 0.345 M HI at the following points. (Assume the titration is done at 25 °C.)
Note that state symbols are not shown for species in this problem.
(a) Before the addition of any HI

(b) After the addition of 15.0 mL of HI

(c) At the titration midpoint

(d) At the equivalence point

(e) After adding 51.9 mL of HI

Determine the pH during the titration of 73.5 mL of 0.429 M acetic acid (K_a = 1.8×10^-5) by 0.429 M KOH at the following points. (Assume the titration is done at 25 °C.)

(a) Before the addition of any KOH

(b) After the addition of 17.0 mL of KOH

(c) At the half-equivalence point (the titration midpoint)

(d) At the equivalence point

(e) After the addition of 110 mL of KOH

Discuss the differences between the IR spectrum of p-bromobenzoic acid and phenylboronic acid with the IR of 4-phenyl benzoic acid.

Could I get an explanation of Henry’s Law including definition, examples, and how it was derivied if possible. I don't want the Wiki link, but I want to understand this law better.

QUESTION 1

Which pair of compounds will form a buffer in aqueous solution?

10 points   

QUESTION 2

A buffer solution is titrated with 0.032 M HCl solution. The initial volume of the buffer is 25.00 mL. The equivalence point of the titration is determined to be 4.88 mL. What is the concentration of conjugate base (in M) in the buffer solution? Assume the stoichiometry of acid to base is 1:1.

10 points   

QUESTION 3

A buffer solution is titrated with 0.046 M NaOH solution. The initial volume of the buffer is 25.00 mL. The equivalence point of the titration is determined to be 8.77 mL. What is the concentration of acid (in M) in the buffer solution? Assume the stoichiometry of acid to base is 1:1.

10 points   

QUESTION 4

The concentrations of acid and conjugate base in a buffer are determined experimentally to be 0.044 M and 0.059 M, respectively. If the total buffer concentration given on the bottle (the true value) is 0.102 M, then what is the percent error of the experimental value?

10 points   

QUESTION 5

There are several calculations that need to be done in order to prepare a specific volume of buffer solution at a particular concentration and pH. There is a worked example in your lab manual on p. 119.

First, determine the correct A^-/HA ratio:  The pK_a of acetic acid is 4.76, and the buffer solution needs to maintain a pH of 4.25. The concentration of acetate (CH₃CO₂^-) should be X times that of the concentration of acetic acid (CH₃CO₂H). What is X?

10 points   

QUESTION 6

There are several calculations that need to be done in order to prepare a specific volume of buffer solution at a particular concentration and pH. There is a worked example in your lab manual on p. 119.

Once the correct ratio of A^- to HA is known, determine the actual concentration of A- needed to make a buffer at a particular concentration.

The ratio of acetate to acetic acid in a buffer is 0.176. That is, the concentration of acetate should be 0.176 times that of the concentration of acetic acid. What is the concentration of acetate (in M) needed to prepare a 0.416 M buffer using acetic acid and acetate?

10 points   

QUESTION 7

There are several calculations that need to be done in order to prepare a specific volume of buffer solution at a particular concentration and pH. There is a worked example in your lab manual on p. 119.

What volume of acetate solution (in mL) is needed to make 250.0 mL of a buffer solution? The concentration of acetate in the buffer must be 0.0594 M, and the concentration of the acetate stock solution is 0.500 M.

The excess Gibbs energy for liquid argon-methane mixtures have been measured at several temperatures. The results are gE/(RT) = xAr(1 ? xAr[A + B(1 ? 2xAr)]
where numerical values for the parameters are given as T(K) = 109.0, A = 0.3024, B = -0.01453 T(K) = 112.0, A = 0.2929, B = -0.01169 T(K) = 115.75, A = 0.2792, B = +0.05115
Compute the following: 1. The activity coefficients of argon and methane at 112.0 K and xAr = 0.5. 2. The molar isothermal enthalpy change on producing an xAr = 0.5 mixture from its pure components at 112.0 K. 3. The molar isothermal entropy change in producing an xAr = 0.5 mixture from its pure components at 112.0 K.

Starting with acetylene develop a synthetic strategy to prepare 2,2,7,7-tetramethyloct-(4E)-ene.  Your answer should include the following.

Stereochemical/regiochemical justification

Mechanistic justification (i.e. where possible show mechanism)

Predict the 1H NMR signals for each step and provide a drawing with values inserted above the appropriate proton.  (Do not predict of consider ions or side-products).

Part A: An acid (HA) dissociates as follows:

HA → H⁺ + A^-

The pH of the 0.25 M solution of HA is 4.64.

What is [A^-]?

Express your answer as a decimal, not an exponent.

Part B:

An acid (HA) dissociates as follows:

HA → H⁺ + A^-

The pH of the 0.88 M solution of HA is 1.91.

What is [HA]?

Express your answer as a decimal, not an exponent.

Part C:

An acid (HA) dissociates as follows:

HA → H⁺ + A^-

The pH of the 0.85 M solution of HA is 1.22.

What is the K_a of HA?

Express your answer as a decimal, not an exponent.

Part D:

A student needs to prepare a buffer solution with a PH of 4.43. Assuming a PKa of 4.70 how many ML of 0.1M B^- would need to be added to 18.0ML of 0.1M HB prepare this buffer?

Part E:

A student needs to prepare a buffer solution with a PH of 5.78. Assuming a PKa of 4.42 how many ML of 0.1M NaOH would need to be added to 18.0ML of 0.1M HB prepare this buffer?

Thank you!

Which of these correctly is identified in terms of increasing 1st ionization energy?

A. C < N < O

B. Ne < P < Mg

C. F < Cl < Br

D. Cs < Na < I

E. Ca < Ba < At