Which is the best HPLC mobile phase solvent to use if the analytes absorb in the UV region of 210 nm? Briefly describe two other mobile phase characteristics that should be considered in HPLC analysis. List two conditions that may cause the HPLC pump pressure to become excessively high and how to resolve it without damaging the pump.

How many ml of both 75% and 5% stock must be combined to prepare 16 ounces of a 25% product?

Answer: [a] ml of 75% stock (#ml) Round to the nearest whole number

Answer: [b] ml of 5% stock (#ml)  Round to the nearest whole number

Consider the following equilibrium: Fe(OH)₃(s) D Fe³⁺(aq) + 3OH^–(aq) with K_sp = 1.6 x 10^-39. The activity coefficients for Fe³⁺(aq) and 3OH^–(aq) are 0.445 and 0.900 in a solution with an ionic strength of 0.01M. The pH of the solution was 11.

a. Calculate [OH^–] in the solution.

b. Use the activity coefficients in order to calculate [Fe³⁺] in the solution.

The initial rate of the reaction of species A and B A + 2 B → C was measured at a temperature of 25 °C for various initial concentrations of A and B. Data are collected in the table. Determine the rate equation from these data. What is the overall order of the reaction? What is the value of the rate constant? (Give the appropriate units of k.)

Calculate ΔG∘rxn for the following reaction:
4CO(g)+2NO2(g)→4CO2(g)+N2(g).
Use the following reactions and given ΔG∘rxn values:
2NO(g)+O2(g)→2NO2(g), ΔG∘rxn= - 72.6 kJ
2CO(g)+O2(g)→2CO2(g), ΔG∘rxn= - 514.4 kJ
12O2(g)+12N2(g)→NO(g), ΔG∘rxn= 87.6 kJ

This question is from a Chemistry lab on constructing a half-potential reduction series. In part A of the lab we must determine if a metal medallion is appropriate or not (could be iron, galvanized, or other appropriate metal). We want to convert Cu^2+ to Cu. How do we determine if the metal is appropriate?

calculate the volume (in milliliters) of 3.0M naoh that must be added to a 1.00M ch3cooh solution to make a buffer having ph of 4.90

A mixture of NH3(g) and N2H4(g) is placed in a sealed container at 310 K . The total pressure is 0.48 atm . The container is heated to 1200 K at which time both substances decompose completely according to the equations 2NH3(g)→N2(g)+3H2(g)  ; N2H4(g)→N2(g)+2H2(g) . After decomposition is complete the total pressure at 1200 K  is found to be 4.5 atm.

Find the percent amount (moles) of N2H4(g) in the original mixture. (Assume two significant figures for the temperature.)

Express your answer using two significant figures.

In which of the reactions below is ΔH not an enthalpy of formation?

Group of answer choices

Both b and c are not enthalpy of formation reactions.

2C(s) + O2(g) → 2CO(g)

Mg(s) + Cl2(g) → MgCl2(s)

Ca(s) + 1/2O2(g) → CaO(s)

C(s) + O2(g) → CO2(g)

All of the following statements are false EXCEPT

Group of answer choices

the frequency of light is directly proportional to the speed of light (in a vacuum).

the wavelength of light is directly proportional to its frequency.

the wavelength of light is directly proportional to the speed of light (in a vacuum).

the frequency of light is inversely proportional to its energy.

the energy of a photon of light is inversely proportional to its wavelength.

Draw the distribution of d electrons for the central atoms in the following molecules using crystal field theory.

K₃[Cr(C₂O₄)₃] 3H₂O (octahedral)

K₂[Cu(C₂O₄)₂] 2H₂O (tertrahedral)

Biochemistry Question:

Understand the role of key metabolites in terms of whether the cell has energy or needs energy (e.g., glucose, acetyl-CoA, ATP, AMP, NAD⁺, NADH)

Meaning, which meabolites indicate that the cell has energy and which indicate that the cell needs energy?

how do you find the wavelength of highest intensity fluorence by looking at the excitation and emission spectrum?

why do some wavelengths show maximum intensity and the rest decrease in fluorescence emission intensity?

In the structure of testosterone, identify all the primary, secondary, tertiary, and quarternary carbons.