To prepare a buffer properly, it is essential to understand how a buffer is described. Here are four buffers used:

1. A solution that is 0.1 M HC2H3O2 and 0.10 M NaC2H3O2

2. One part 0.10 M NH3 mixed with one part 0.10 M NH4Cl

3. A solution that is 0.10 M NH3 and 0.20 M NH4Cl

4. Three parts 0.10 M NH3 mixed with one part 0.10 M HCl

For the first and third buffers, the concentrations of each component are explicit. What are the identities of and concentrations of the buffer components in the second and third buffers? (Keep in mind when mixed, the original solutions dilute each other)

Buffer 2:

Buffer 4:

In paper chromtography, what is the nature of the attractions between the stationary phase (cellulose) and the moving phase (hydrochloric acid/water/acetone) and the species ( Zn2+, Co2+, Cu2+, Cd2+ , Fe3+, and Ni2+ in two unknown solutions)  being separated, in particular what affects the Rf values and how?

Note: Filter paper (Whatman #1) serves as the stationary phase, and the mobile phase consists of a mixture of acetone and 6 M hydrochloric acid. A single spot of the mixture to be analyzed is applied near one edge of a sheet of filter paper. A spot of solution containing each of the cations that might be in the unknown mixture is also placed near the edge of the same sheet for comparison. The treated strip is then placed in a covered jar or beaker (which acts as a developing chamber) containing a shallow layer of the solvent mixture (see Figure 3). Since filter paper is very permeable to the solvent, the solvent begins to rise up the strip by capillary action. The various spots on the developed chromatogram will be highlighted by treatment with several chemical reagents to enhance their color. The reagents to be used are ammonia, dimethylglyoxime (DMG), and 8–hydroxyquinoline (oxine)

Derive an equilibrium relationship (y = f (x)) with relative volatility in the ideal solution

Determine the number of translational, rotational and vibrational degrees of freedom of HCl, CO2, H2O, NH3, and CH4.

Write net ionic equations for the reactions that take place when aqueous solutions of the following substances are mixed.

A) sodium cyanide and nitric acid

B) ammonium chloride and sodium hydroxide

C) sodium cyanide and ammonium bromide

D) sodium hydrogen sulfite and potassium cyanide

E) sodium hypochlorite and ammonia

A solution is 0.020 M in each Ca²⁺ and Cd²⁺. Adjusting the pH of the solution to which of the following values would achieve the best separation by precipitation of the hydroxides? solubility product constants

Best pH =  ---Select--- 13.0 12.5 12.0 11.5 11.0 10.5 10.0 9.5 9.0 8.5 8.0

What would be the resulting concentrations of the ions if the solution were adjusted to this pH?

[Ca²⁺] =  M

[Cd²⁺] =

M

Based on your copper solid used in RXN 1, how many grams of copper product should have been formed? Based on the copper solid in RXN 1, how many grams of the copper Hydroxide should have been formed in RXN 2? Based on the mass of copper used in RXN 1, how many grams of the zinc metal should have been used in RXN 5?

My mass of copper in RXN 1: .3595 grams

RXN1 : 4HN0₃ (aq) + Cu(s)-> Cu(NO₃)₂(aq) + 2H₂O (l) + 2NO₂ (g)

RXN 2: Cu(NO₃)₂(aq) + 2NaOH(aq) -> Cu(OH)₂(s) + 2NaNO_3(aq)

RXN 5: CuSO_4(aq)+ ZN(s) -> Cu (s) + Zn SO₄ (aq)       ( Mass of zinc in RXN 5: 3.00g)

Please show all work. I am confused on how to do this.

Calculate the expected ph of the following solutions. Please show all of your work and explain your steps, if you can.

Solution 1: 50mL 0.10M NH3 + 50mL 0.10M NH4NO3

Solution 2: 10mL solution 1 + 5mL H2O + 1mL 0.10M HCl

Solution 3: 10mL solution 1 + 6mL 0.10M HCl

Solution 4: 10mL solution 1 + 5mL H2O + 1mL 0.10M NaOH

Please write legibly so I can see what steps you took!

Rank the following photons in terms of increasing energy. (Use the drop down options, and choose '1' for the lowest photon energy, '2' for the next lowest, etc.) Yellow (λ = 590 nm) Red (λ = 680 nm) Blue (λ = 443 nm) Microwave (ν = 7.5×1011 Hz) Ultraviolet (ν = 8.7×1015 Hz)

A reaction
A(aq) + B(aq) --> C(aq)
has a standard free-energy change of –3.23 kJ/mol at 25 °C. What are the concentrations of A, B, and C at equilibrium if, at the beginning of the reaction, their concentrations are 0.30 M, 0.40 M, and 0 M, respectively?

A 3.0% by mass aqueous solution of hydrogen peroxide (H2O2) can be purchased at a pharmacy; by contrast, chemistry departments can purchase 30.0% by mass aqueous solution of hydrogen peroxide having a density of 1.10 g/mL at 25°C.

How many moles of hydrogen peroxide are supplied by 2.00 g of the 30.0% solution at 25°C?

How many moles of hydrogen peroxide are supplied by 2.00 mL of the 30.0% solution at 25°C.

What mass in grams of water is present in 2.00 mL of the 30.0% solution at 25°C?

How many hydrogen peroxide molecules are present per milliliter of the 30.0% solution at 25°C?

A 7.95-atm PCl₅ is initially placed in an empty vessel at 25˚C. Calculate K_p if the equilibrium partial pressure of Cl₂ is 3.00 atm at the same temperature.

I am completely lost on how to even start the problem, let alone solve it.

This is for the lab practical I take on Tuesday night. If you could answer each one and show your work/ explain that'd be amazing so I can do well on the actual practical on Tuesday! Thank you!

Chemistry 211   Lab Final Study Guide   Spring 2015

Useful Information:
1 ampere =coulomb/sec
Faraday’s constant = 96,500 coulombs/mole of electrons
Molar mass of Au = 197.0 g/mole, Molar mass of Cu = 63.55 g/mole
m = moles ,   '   ’

c   kg

ΔTf

= Tf

− Tf

where Tf is for the pure solvent and Tf

is for the mixture.

ΔT = (K

)(m ) ,

m = (

(mass of

solute, g )
)(   ).

f   f   c

c   molar

mass, g

mol −1

mass of

solvent, kg

7.   Next question

(a)   If you weigh 6.355 grams of copper, add concentrated nitric acid to dissolve it, and then dilute the solution to a total volume of 50 mL, how many moles of copper are in this solution?

(b)   For the equilibrium reaction 3H2(g) + N2(g) → 2NH3(g), what is the equilibrium constant expression, Kc, for this reaction? (5pts)

8.   Suppose at some temperature, the equilibrium concentration of H2 is 0.45M, the equilibrium concentration of N2 is 0.38M, and the equilibrium concentration of NH3 is 0.42M. What is the value of the equilibrium constant for the reaction 3H2(g) + N2(g) → 2NH3(g) at this temperature? (Show your work. No credit will be given if your work is not shown.)

9.   Next question
(a)   If you need 0.0534 moles of NaOH to reach equivalent point in the titration with acetic acid, how many mL of 0.09876M NaOH will you need?

(b)   The Ksp of Cu(OH)2 is 2.2x10-20, what is the solubility of Cu(OH)2?

10.   Next question
(a)   In non-sulfide qualitative analysis of representative cations, the Group A cations comprising of Pb2+,

Hg2+, and Ag+ give a precipitate with   solution.
(b)   From a solution containing mixture of Pb2+, Fe3+, and Al3+, Pb2+ is removed by adding HCl solution. To the remaining cation mixture, on making the solution basic with NH3 (pH=9 – 10), both the cations form precipitate. Further analysis of the cation mixture containing Fe3+ and Al3+ is carried out by adding NaOH solution.

Aluminum hydroxide    (dissolves/remains undissolved) in NaOH solution while Ferric hydroxide        ( dissolves/remains undissolved).
(c)   Fe(OH)3 precipitate is dissolved in minimal amount of aqueous HCl which gives a

yellow solution. To this solution addition of    solution (at pH = 4 – 5) yields a dark blue solid known as Prussian Blue.

(d)   Describe the method for checking for completeness of precipitate in qualitative analysis of ions.

Which of the following statements is false?