1/ Calculate the volume of 0.280-M NaOH solution needed to completely neutralize 27.4 mL of a 0.560-M solution of the monoprotic acid HBr.

2/ To determine the molar mass of an organic acid, HA, we titrate 1.047 g of HA with standardized NaOH. Calculate the molar mass of HA assuming the acid reacts with 37.17 mL of 0.469 M NaOH according to the equation

HA(aq) + NaOH(aq) → NaA(aq) + H₂O(ℓ)

3/

2 NaBH₄(aq) + H₂SO₄(aq) → 2 H₂(g) + Na₂SO₄(aq) + B₂H₆(g)

What volume, in mL, of a 0.504 M solution of NaBH₄ is required to produce 0.539 g of B₂H₆? H₂SO₄ is present in excess.

please help me with all the questions i really need help to prepare for final!

Why is platinum the element of choice to study the trans effect?

31. What is the initiator in the polymerization of isobutylene? 


32. What is the general name of the product produced by cationic initiation? 


33. What reactant besides the monomer is present in cationic chain propagation reactions? 


explain the observed absorption maxima of each of the following molecules:

a) nitrobenzene, 252 nm

b) 2-nitrotoluene, 250 nm

c) 2-isopropylnitrobenze, 247 nm

d) 2-t-butylnitrobenzene, no peak

They are all being observed in UV-vis spectroscopy (200 - 800 nm)

In addition to this, the question also asks to provide 3D structures which i think i have a grasp of. I dont know, however, if they are necessary to answer this question but i am lost on explaining the absorption maximas.

Thank you in advance!

In each of the following balanced oxidation-reduction equations, identify those elements that undergo changes in oxidation number and indicate the magnitude of the change in each case

Part A

2MnO4−(aq)+3S2−(aq)+4H2O(l)→3S(s)+2MnO2(s)+8OH−(aq)

Enter your answers as chemical symbols separated by a comma.

Part C

4H2O2(aq)+Cl2O7(g)+2OH−(aq)→2ClO2−(aq)+5H2O(l)+4O2(g)

Enter your answers as chemical symbols separated by a comma

Ba2+(aq)+2OH−(aq)+H2O2(aq)+2ClO2(aq)→Ba(ClO2)2(s)+2H2O(l)+O2(g)

Enter your answers as chemical symbols separated by a comma

A certain weak acid, HA , has a Ka value of 2.2×10⁻⁷.

Part A

Calculate the percent ionization of HA in a 0.10 M solution.

You are searching for an inexpensive synthetic route to make anthraquinone to use it as the active component in a new laxative formulation. Reaction of benzene and phthalic anhydride yielded a yellow solid thought to be anthraquinone. Combustion analysis of 0.520 g of the yellow solid yielded 1.54 g of carbon dioxide and 0.180 g of water; (all carbon dioxide and water formed by combustion were isolated and weighed). In another experiment, the molar mass of the yellow solid was found to be approximately 205 g/mol. Use the analysis information above to determine the molecular formula of the yellow solid.

At 300K, the vapor pressure of pure liquid A and liquid B are 37.33 kPa and 22.66 kPa respectively. If we mix 2 mol liquid A with 2 mol liquid B, the total vapor pressure above the solution is 50.66 kPa and the molar fraction of vapor A is 0.60. Assume the vapor is an ideal gas. Calculate (a) the activity of A and B in the solution (b) the Gibbs energy change of mixing ΔmixG (c) If the solution is an ideal solution, what’s the number of ΔmixGid?

What mass of a solid hydrate of iron (III) sulfate that is 76.3% by mass iron (III) sulfate is needed to supply 1.00 g of iron (III) ion? How many moles of carbon atoms are present in 2.41 x 1022 molecules of acetic acid? How many chloride ions are supplied by 1.00 g of chromium (III) chloride hexahydrate? What mass in grams of cobalt(II) nitrate hexahydrate supplies 0.200 g of cobalt (II) nitrate? What mass in grams of oxalic acid dihydrate supplies 3.01 x 1021 oxygen atoms?

On a day with a temperature of 15 ∘C and a pressure of 792.0 torr , how many grams of peroxyacyl nitrates are found in the air above Los Angeles (1500. km3) if the concentration is 30.0 ppb by moles? The molar mass of the major peroxyacyl nitrate, peroxyacetyl nitrate, is 118.03 g/mol.

Calculate the pH after adding 5.00 mL of 0.15 M HNO₃ to 250 mL of an acetic acid/acetate buffer with an initial pH of 4.32 and a total buffer concentration of 0.25 M. Neglect activity coefficients for this problem.

The specific rotation, [α]D, for (-)-2-butanol is +14. What is the observed rotation for a solution of 1.0 g of (-)-2-butanol in 10 mL of water in a sample tube having a pathlength of 10 cm? ??????degrees .

The observed rotation of a solution of 1.5 g of a compound in 10 mL of water is +3.4 degrees. If the pathlength is 10 cm, what is the specific rotation of the compound? .

Introduction: In this experiment, the following equilibrium system will be observed:

Fe⁺³_(aq)   +   SCN^-_(aq)   ↔   Fe(SCN)⁺²_(aq)

The reactants are both colorless solutions (the ferric ion is slightly colored, but it is treated with nitric acid to remove the color) while the product has a reddish color. The intensity of the color that is produced is directly proportional to its concentration. If a light source is allowed to shine through such a solution, it is found that the amount of light absorbed (i.e. the energy that is not being transmitted through the solution) is also directly proportional to the concentration of the solution. A spectrophotometer is a device that will shine light through a sample and measure the percent of light that is transmitted and absorbed. These data can be used to determine the equilibrium concentrations in a system by applying Beer’s Law.

            Beer’s Law:   absorbance = ab[colored species]

a = molar absorptivity coefficient of the colored species (constant for a particular wavelength)

b = thickness of the cell used in the measurement

[colored species] = molar concentration.

            Since the same cell will be used throughout the experiment as well as the same wavelength, both a and b will be constants and they will be combined into a single constant labeled Z. Therefore:

                        absorbance = Z[colored species]

Procedure:

A.Preparation of Solutions: Place 6 test tubes in a test tube rack labeled 1-6. Add the reagents listed below using pipettes (pipettes are to be cleaned and prepared in the same manner as a buret). Note that the total volume in each test tube is 20.0 mL.

B.Calibrating the spectrophotometer:

1.Set the wavelength to 447 nm.

2.Rinse a cuvet (small disposable test tube) with distilled water. Fill the cuvet with distilled water and wipe the outside of it with a paper towel to remove any liquid and fingerprints. From this point on, handle the cuvet by the rim only.

3.Insert the cuvet into the sample compartment and press the green calibration button.

C.Determining the Value of Z: The value of Z is determined by measuring the absorbance of a solution of known concentration ( absorbance = Z[colored species] ).   The solution of known concentration was prepared by adding 5.00 mL of .00200 M NaSCN and 25.0 mL of .200M Fe(NO₃)₃ and was diluted to a volume of 100.0 mL. From these quantities it is evident that the ferric nitrate is in extreme excess which forces the equilibrium to the right. It can be assumed that the magnitude of the excess reactant causes the reaction to go to completion. From this information, calculate the concentration of the Fe(SCN)⁺² in the solution. Rinse a cuvet with water and with the solution to be tested. Fill the cuvet with the known concentration solution and insert it into the sample compartment. Record the absorbance value and calculate the value of Z.

D.Determining the Absorbance of the Equilibrium Mixtures: Determine the absorbance for each of the five solutions. Be sure to clean the cuvet each time with distilled water, rinse it with the solution to be tested, and thoroughly wipe the outside of the cuvet.

Data and Calculations:

1. Known Concentration Solution

                        Concentration of Fe(SCN)⁺² : ____________    

                                    show work

Absorbance: 0.424

                        Z: ____________________

                                    show work

            2. Equilibrium Solutions

Given the measured absorbance for test tube 2, show the work for the calculations for each of the concentrations requested in the table above. Record the concentrations for all the test tubes in the table above, but only show the work for test tube 2.

                        [Fe(SCN)+2]

Initial [Fe⁺³]                                            Equilibrium [Fe+3]

Initial [SCN^-]                                          Equilibrium [SCN^-]

Write the expression for K_c for this reaction.

Calculate the value of K_c for each of the five equilibrium mixtures and calculate the average. Show the work for test tube 2 only.

            t.t. 1:   K_c = ____________                t.t. 2:   K_c = ____________

t.t. 3:   K_c = ____________                t.t. 4:   K_c = ____________

t.t. 5:   K_c = ____________                Average K_c =___________

Using 131 as the accepted value for K_c, determine the percent error.