An analytical chemist decides to analyze a given sample spectrophotometrically for its copper content.  The chemist knows that copper(I) ions form a colored coordination complex with neocuproine (ncup), C₁₄H₁₂N₂, in a one-to-two ratio, Cu(ncup)₂⁺.  The chemist also knows that Cu(ncup)₂⁺ is more soluble in 3-methyl-1-butanol than in water and that Cu(ncup)₂⁺ in 3-methyl-1-butanol shows an absorbance maximum at 454 nm.  Thus, the chemist proceeds with the chemical analysis.  She treats 0.1482 g of copper wire, 98.50% (w/w) pure, with a minimum volume of concentrated nitric acid in order to get all of the copper metal into solution (aqueous) as copper (II) ions.  After neutralizing the copper-containing solution with base, the chemist transfers the solution quantitatively to a 500.0-mL volumetric flask and then dilutes the solution with deionized water up to the mark on the flask.  Next, the chemist treats 10.00 mL of the solution with a reducing agent in order to convert copper(II) ions to copper(I) ions and then adds a buffer in order to change the pH of the solution to one for which complexation between copper(I) ions and neocuproine occurs readily.  Subsequently, the chemist treats the resulting solution with neocuproine to complex all of the copper(I) ions and then adds 100.00 mL of 3-methyl-1-butanol.  After shaking well to make sure that essentially all of the Cu(ncup)₂⁺ is extracted by the 3-methyl-1-butanol from the aqueous solution, the chemist separates the aqueous layer (bottom) completely from the 3-methyl-1-butanol layer (top) and then quantitatively transfers the 3-methyl-1-butanol layer to a 1.000-L volumetric flask, diluting the solution with 3-methyl-1-butanol up to the mark on the flask.  Using a spectrophotometer, the chemist finds the percent transmittance of the final 3-methyl-1-butanol solution in a 2.00-cm cuvet is 18.8 at 454 nm.  The chemist then prepares the sample.  She treats 0.2990 g of the previously dried copper oxide sample with a minimum volume of concentrated sulfuric acid in order to get all of the copper into solution (aqueous) as copper(II) ions.  After neutralizing the copper-containing solution with base, the chemist transfers the solution quantitatively to a 500.0-mL volumetric flask and then dilutes the solution with deionized water up to the mark on the flask.  Next, the chemist treats 10.00 mL of the solution with the reducing agent and then adds the buffer.  Subsequently, the chemist treats the resulting solution with neocuproine and then adds 100.00 mL of 3-methyl-1-butanol.  After shaking well to make sure that essentially all of the Cu(ncup)₂⁺ is extracted by the 3-methyl-1-butanol from the aqueous solution, the chemist separates the aqueous layer (bottom) completely from the 3-methyl-1-butanol layer (top) and then quantitatively transfers the 3-methyl-1-butanol layer to a 500.0-mL volumetric flask, diluting the solution with 3-methyl-1-butanol up to the mark on the flask.  Using a spectrophotometer, the chemist finds the percent transmittance of the final 3-methyl-1-butanol solution in a 2.00-cm cuvet is 27.6 at 454 nm.  Find the percent by mass of copper in the sample analyzed by the analytical chemist.

Consider the following reaction: S↔P where the rate constant for the forward reaction is k₁, and the rate constant for the reverse reaction is k₂, and Keq= [P]/[S]

Which of the following would be affected by an enzyme? Please answer yes or no and give a short explanation (5-20 words maximally)

a) decreased K_eq

b) increased k₁

c) increased Keq

d) increased Δ G^#

e) decreased Δ G^#

f) increased k₂

g) more negative Δ G⁰

When 6.104 grams of a hydrocarbon, CxHy, were burned in a combustion analysis apparatus, 19.15 grams of CO2 and 7.842 grams of H2O were produced. In a separate experiment, the molar mass of the compound was found to be 28.05 g/mol. Determine the empirical formula and the molecular formula of the hydrocarbon.

A 7.797 gram sample of an organic compound containing C, H and O is analyzed by combustion analysis and 7.623 grams of CO2 and 1.561 grams of H2O are produced. In a separate experiment, the molar mass is found to be 90.04 g/mol. Determine the empirical formula and the molecular formula of the organic compound.

Complete and balance the following equations. (Use the lowest possible coefficients. Include states-of-matter under SATP conditions in your answer.)

A) H₂O₂(aq) + Cl₂O₇(aq) → ClO₂⁻ (aq) + O₂(g) (basic solution)
B) Cr₂O₇^2-(aq) + I ⁻ (aq) → Cr³⁺(aq) + IO₃⁻ (aq) (acidic solution)

C) MnO₄⁻ (aq) + Cl  ⁻ (aq) → Mn²⁺(aq) + Cl₂(g) (acidic solution)

why do we not need to determine the exact volume of water needed to make the solution with the KHP in the standardization titration?

Calculate the partial pressure (in atm) of CH₃Br at equilibrium when 2.01 atm of CH₃OH and 2.01 atm of HBr react at 1000 K according to the following chemical equation:

K_p = 2.78

When 6.104 grams of a hydrocarbon, CxHy, were burned in a combustion analysis apparatus, 19.15 grams of CO2 and 7.842 grams of H2O were produced. In a separate experiment, the molar mass of the compound was found to be 28.05 g/mol. Determine the empirical formula and the molecular formula of the hydrocarbon.

A 7.797 gram sample of an organic compound containing C, H and O is analyzed by combustion analysis and 7.623 grams of CO₂ and 1.561 grams of H₂O are produced.
In a separate experiment, the molar mass is found to be 90.04 g/mol. Determine the empirical formula and the molecular formula of the organic compound.

3. A student makes a solution for analysis by mixing 5.172 grams of Cu_{2SO4 into 500 grams of water. The density of water at the temperature of the lab at the time the solution was made is 0.9926 g/mL. Calculate the molarity, molality, mole fraction, and mass percent of the copper 1 sulfate. Show all work.}

_{1. The presence of a dirty fingerprint on the cuvette during measurement of the sample solution resulted in the absorbance being reported incorrectly. Do you think the number reported was too high or too low? Explain why.}

_{2. List the important sources of error in this experiment and what effect each would have on the results. Discuss in particular any errors that you may have made include at least 3 ( with specific implications) for full credit.}

_{( PLEASE SHOW ALL WORKINGS AND SOLUTIONS)}

A student must make a buffer solution with a pH of 1.00.

Determine which weak acid is the best option to make a buffer at the specified pH.

formic acid,K_a = 1.77 x 10⁻⁴, 2.00 M

sodium bisulfate monohydrate, K_a = 1.20 x 10⁻², 3.00 M

acetic acid, K_a = 1.75 x 10⁻⁵, 5.00 M

propionic acid, K_a =1.34 x 10⁻⁵, 3.00 M

Determine which conjugate base is the best option to make a buffer at the specified pH.

sodium acetate trihydrate, CH₃COONa⋅3H₂O

sodium propionate, CH₃CH₂COONa

sodium sulfate decahydrate, Na₂SO₄⋅10H₂O

sodium formate, HCOONa

The final volume of buffer solution must be 100.00 mL and the final concentration of the weak acid must be 0.100 M.
Based on this information, what mass of solid conjugate base should the student weigh out to make the buffer solution with a pH of 1.00?

mass = Answer g

Based on this information, what volume of acid should the student measure to make the buffer solution?

volume = Answer mL

A mixture of H2 and He are in a 10.0 L vessel at 273 K. The total pressure is 756 torr. What is the partial pressure of H2 in the vessel if XHe = 0.75?

Buffer capacity is a measure of a buffer solution's resistance to changes in pH as strong acid or base is added. Suppose that you have 145 mL of a buffer that is 0.100 M in both propanoic acid (C2H5COOH) and its conjugate base (C2H5COO−). Calculate the maximum volume of 0.420 M HCl that can be added to the buffer before its buffering capacity is lost.

list 3 reasons you would use hplc instead of gc for organic compounds

NMR Spectroscopy Question

Given the compound: C₁₈H₂₄O₃

_{And the information of the Hydrogen and Carbon NMR Spectroscopy}

¹H: 10.1, doublet, 1; 7.2, singlet, 1; 2.4, quartet, 1; 1.5, quint, 2; 1.2, t, 3

¹³C: 199, 130, 125, 31, 23, 20

1. Calculate degree on unsaturation

2. Draw 1H and 13C NMRs. Assign a fragment to each peak and justify your choice using tools such as the N+1 rule

3. Draw a structure of your unknown

4. If there is more than one structure possible for your unknown please show both and justify our choice.

This is all the given information.