What is the pH of a 0.136 M monoprotic acid whose Ka is 5.7 10-4?

3. Consider the following possible ligands. For which of these do you expect back-bonding to be significant in their complexes? For those that you do not expect to participate in back-bonding, explain why.

H2       CO       Br2       O2       NO

A liter of pH 7.20 phosphate buffer is needed for a certain experiment. The Henderson-Hasselbach equation will be sufficiently accurate for your determination of pH. The pK’s for possibly relevant phosphate species are:

H3PO4 ↔ H2PO4- + H+ pK = 2.15

H2PO4- ↔ HPO4-2 + H+ pK = 7.20

HPO4-2 ↔ PO4-3 + H+ pK = 12.4

0.100 Moles of H3PO4 were dissolved in about 800 mL of water, and the pH was adjusted to 7.20 using a standardized pH meter and a 1 M solution of KOH followed by addition of water to a volume of 1.00 L.

a. (10 pts) Write the equation for the charge balance to show how [K+], [H2PO4-], and [HPO4-2] are related. ([H+] and [OH-], although they are charged species, can be neglected for charge balance when compared to [K+], [H2PO4-], and [HPO4-2])

b. (10 pts) At pH 7.20 what is the ratio of [H2PO4-] to [HPO4-2]?

c. (20 pts) Combine your findings from parts a and b to determine how many mL of 1 M KOH must be added. {An important hint: By mass balance, the total molar concentration of phosphate species at pH 7.2 must equal the total molar concentration of phosphate species that was added from H3PO4.}

PLEASE ANSWER ALL PARTS, I NEED HELP. THANKS IN ADVANCE!

I have to estimate, to the nearest degree, the temp. at which the vapor pressure of a solution (3.9g benzene, 4.6g toluene) reaches 1 atm. I believe the mole fractions are .73 for benzene, and .26 for toluene.

A 25.0 mL sample of 0.125 molL−1 pyridine (Kb=1.7×10−9) is titrated with 0.100 molL−1HCl.

Part A

Calculate the pH at 0 mL of added acid.

Express your answer using two decimal places.

Part B

Calculate the pH at 10 mL of added acid.

Express your answer using two decimal places.

Part C

Calculate the pH at 20 mL of added acid.

Express your answer using two decimal places.

Part D

Calculate the pH at equivalence point.

Express your answer using two decimal places.

Part E

Calculate the pH at one-half equivalence point.

Express your answer using two decimal places.

Part F

Calculate the pH at 40 mL of added acid.

Express your answer using two decimal places.

Part G

Calculate the pH at 50 mL of added acid.

Express your answer using two decimal places.

The pKb values for the dibasic base B are pKb1 = 2.10 and pKb2 = 7.59. Calculate the pH at each of the following points in the titration of 50.0 mL of a 0.85 M B(aq) with 0.85 M HCl(aq).

(a) before addition of any HCl (b) after addition of 25.0 mL of HCl (c) after addition of 50.0 mL of HCl (d) after addition of 75.0 mL of HCl (e) after addition of 100.0 mL of HCl

The reaction of nitric oxide (NO(g)) with molecular hydrogen (H2(g)) results in the formation of nitrogen and water as follows: 2NO (g) + 2H2(g)...> N2(g) + 2H2O(g) The experimentally determined rate-law expression for this reaction is first order in H2(g) and second order with NO(g).

a) Is the reaction above, as written an elementary reaction?

b) One potential mechanism for this reaction is as follows: H2(g) + 2NO(g)...> N2O (g) + H2O (g) k1 H2(g) + N2O (g)...> N2(g) + H2O(g) k2 Is this mechanism consistent with the experimental rate law? If not, why?

c) An alternative mechanism for the reaction is:

2NO(g) <...> N2O2(g) (fast) k1(fwd) k-1(rev) H2(g) + N2O2 (g)...> N2O(g) + H2O(g) k2 H2(g) + N2O (g)...> N2(g) + H2O(g) k3

Show that this mechanism is consistent with the experimental law.

I need a good explanation for just part b please

BIOCHEM

PLEASE ONLY ANSWER IF YOU TRULY UNDERSTAND IT!! I posted this many times, and people have been giving wrong answers. Also ONLY answer if you can answer it correctly and FULLY. Also a brief explanation helps! Thank you!

2) The double helix of B-form DNA is stabilized most significantly by:

A) nonspecific base-stacking interactions between two adjacent bases in the same strand

B) hydrogen bonding between the phosphate groups of two side-by-side strands

C) covalent bonds between the 3’-end of one stand and the 5’-end of the other

D) hydrogen bonds between the ribose of each strand

3) The DNA oligonucleotide abbreviated 5’-pATCGAC-3’ (the p indicated a phosphate on the 5’-end):

A) has an A at its 3’ end

B) has 6 phosphate groups

C) has a phosphate on its 3’ end

D) violates Chargaff’s rules

4) Which of the following is a palindromic sequence?

A) GGATCC

B) GTATCC

C)GAATCC

D) CCTTCC CCTAGG CATAGG CTTAGG GGAAGG

6) What is the principal effect of UV light on DNA?

A) melting of B-form helices

B) production of T-dimers

C) deamination of cytosine residues

D) oxidation of guanosine residues

7) Chargaff’s rules state that in typical DNA:

A) A = G

B) A = C

C) A + T = G + C

D) A + G = T + C

8) In the Watson-Crick structure of DNA, the:

A) nucleotides are arranged in the A-form

B) 2’-hydroxyl groups in ribose sometimes participate in hydrogen bonding

C) two strands are antiparallel

D) purine content must be the same in both strands

9) The recognition site of some restriction enzymes are listed below. Which will not produce a “sticky end”?

A) GA↓ATTC

B) CCC↓GGG

C) C↓TCGCG

D) all will produce “sticky ends”

10) Proteins that cut DNA to unwind it are called:

A) helicases

B) topoisomerases

C) ligases

D) endonucleases

Why is H₂ more acidic than NH₃?

Calculate the theoretical and percent yield of terephthalic acid, based on PET being the limiting reagent.

MW terephthalic acid= 166.13 g/mol

MW PET= 192 g/mol

Mass of product = 0.76 g

To a 150.0mL volumetric flask are added 1.00 mL volumes of three solutions: 0.0100 M AgNO_3, 0.225 M NaBr, and 0.100 M NaCN. The mixture is diluted with deionized water to the mark and shaken vigorously. What mass of AgBr would precipitate from this mixture? (Hint: The K_sp of AgBr is 5.4x10^-13 and the K_f of Ag(CN)₂^- is 1.0x10²¹)

Consider the reaction of I2 (g) described by I2 (g) = 2 I (g). The total pressure and partial pressure of I2 (g) at 1400⁰C have been measured to be 36.0 torr and 28.1 torr, respectively. Use these data to calculate KP⁰, K⁰c, and Kx at 1400⁰C. Calculate xI under these conditions? What would X₁ be if we decreased the total pressure to 36.0×10-6 torr? What would X₁ be if we increased the total pressure to 36.0 atm?