What is the difference between the Normal Hydrogen Electrode (NHE) and the Reversible Hydrogen Electrode (RHE)?

- Also, if a redox happens at the NHE of 0.2 V, please calculate the potential for the RHE at pH = 1.

The reaction below has an equilibrium constant K p =2.2× 10 6 at 298 K. 2 COF 2 (g)⇌ CO 2 (g)+ CF 4 (g) Part A Calculate K p for the reaction below. COF 2 (g)⇌ 1 2 CO 2 (g)+ 1 2 CF 4 (g) Part B Calculate K p for the reaction below. 2 3 COF 2 (g)⇌ 1 3 CO 2 (g)+ 1 3 CF 4 (g) Part C Calculate K p for the reaction below. 2 CO 2 (g)+2 CF 4 (g)⇌4 COF 2 (g)

You are asked to prepare 500. mL of a 0.300 M acetate buffer at pH 4.90 using only pure acetic acid (MW=60.05 g/mol, pKa=4.76), 3.00 M NaOH, and water. Answer the following questions regarding the preparation of the buffer.

What volume of 3.00 M NaOH must you add to the acetic acid to achieve a buffer with a pH of 4.90 at a final volume of 500 mL? (Ignore activity coefficients.)

Copper salts – Assume that, in this question, the cation-to-anion size ratio should be in the 0.25 – 1 range and that all compounds adopt cubic cells. a) The chloride atoms are in tetrahedral holes in copper(I) chloride (Copper has +1 charge). Draw the unit cell of copper(I) chloride. b) Propose a unit cell for copper(II) chloride (Copper has +2 charge) and draw. c) Determine the coordination numbers for copper and chloride atoms in copper(II) chloride. d) Compare the densities of copper(I) chloride and copper(II) chloride. e) Compare the lattice parameters for copper(I) chloride and copper(II) chloride. f) Propose a unit cell for copper(I) sulfide (Copper has +1 charge) and draw. g) Determine the coordination numbers for copper and sulfide atoms in copper(I) sulfide.

Define reaction rate. Distinguish between the initial rate, average rate, and instantaneous rate of a chemical reaction. which of these rates is usually fastest? The initial rate is the rate used by convention. Give a possible explanation as to why?

(I have defined all rates. I am mainly stumped on which rate is the fastest and why initial rate is used by convention)

Another unknown was tested using this procedure. Upon the addition of 6M NH3 and 6M HNO3, no precipitate formed. (NH4)2CO3 was then added. A precipitate formed and the mixture was centrifuged and decanted. The liquid was then transferred to a small beaker and heated to dryness. Once cool, 1M H3PO4 and 1M Na2HPO4 were added to re-dissolve the solid, and the solution was divided into two test tubes. To the first, solid KI was added; no change was observed. To the second, HDMG was added; a red precipitate formed. The solid from the centrifugation was then dissolved in 6M HCl and Na2SO4 was added. A white precipitate formed. The mixture was centrifuged and decanted. 6M NH3 and (NH4)2C2O4 were added to the liquid. A white precipitate formed. Which cations are present in the unknown?

One excited state of the sodium atom lies at 25, 739.86 cm-1 above the ground state, another lies at 50 266.88 cm-1. Suppose they are connected by a perturbation equivalent in energy to (a) 100 cm-1 , (b) 1000 cm-1 , (c) 5000 cm-1 . Calculate the energies and composition of the states of the perturbed system.

The deprotonation of acetic acid goes by the mechanism

CH₃COOH + H₂O ⇒ CH₃COO^– + H₃O⁺

Assume the pKa of acetic acid at 25°C is 4.76, and the forward rate at a pH of 4 is 102 s^–1.

(a) Calculate the forward and reverse rate constants for the reaction.

(b) Calculate the relaxation time if a 10^–2 M solution of solution of acetate in water at pH 6 is subjected to a temperature jump.

(c) Given reasonable estimates for molecular sizes, determine if the forward and/or the reverse reactions are likely to be diffusion limit.

a) Describe the differences between ionization energy, work function and electron affinity.

b) Show their location with respect to Evac on a band diagram.

The density of a gas is 1.76g/L at 1 atm and 10 °C. What is its density at 1.5 atm and 20 °C?

A. 4.65g/L

B. 3.23g/L

C. 1.52g/L

D. 2.15g/L

E. 2.55g/L

For questions 13-14, use the information provided below from the experiment Identification of an Unknown. The molecular masses and reactions are provided for you.

NaHCO₃          KHCO₃                        Na₂CO₃                        K₂CO₃              NaCl                KCl          

84.01 g/mol     100.12 g/mol   105.99 g/mol   138.21 g/mol   58.44 g/mol     74.55g/mol

2 NaHCO₃ (s) à Na₂CO₃ (s) + H₂O (g) + CO₂ (g)                    (Reaction 1)

Na₂CO₃ (s) +2HCl (aq) à 2NaCl (s) + H₂O (l) + CO₂ (g)         (Reaction 2)

13.       Brad starts with 0.652 g of unknown. How much mass should he have after the first heating step if his unknown
            was NaHCO₃?

            A.        0.411 g Na₂CO₃

            B.         0.326 g Na₂CO₃

            C.         0.822 g Na₂CO₃

            D.        0.00402 g Na₂CO₃

14.       If Brad has a final mass of 0.270 g at the end of the experiment (after the 2^nd heating), what is his percent yield
            of the final salt? (Assuming he starts with 0.652 g of NaHCO₃).

            A.       40%

            B.         60%

            C.         80%

            D.        86%

           

15.       What is the concentration of chloride ions in 50.0 mL of a 5.25 M solution of barium chloride?

            A.        0.525 M Cl^-

            B.         1.05 M Cl^-

                C.         5.25 M Cl^-

            D.        10.5 M Cl^-

Aqueous Solutions

16.       Which of the following represents a correct precipitation reaction between sodium iodide and lead(IV) sulfate?

            A.        PbSO₄ (aq) + NaI(aq) à PbI (aq) + NaSO₄ (aq)

            B.         PbSO₄ (aq) + NaI(aq) à PbI (s) + NaSO₄ (aq)

            C.         Pb(SO₄)₂(aq) + NaI (aq) à PbI₂ (s) + Na₂SO₄ (aq)

            D.        Pb(SO₄)₂(aq) + NaI (aq) à PbI₂ (aq) + Na₂SO₄ (aq)

17.       How many of the following salts would not form a precipitate in an aqueous solution?

A.       one

B.        two

C.         three

D.        four

18.       What type of reaction is the following?           CaCO₃ + heat à CaO + CO₂

            A.        Combination

            B.         Decomposition

            C.         Single Replacement

            D.        Combustion

19.       Calculate the amount of copper recovered from an 85% yield if the theoretical yield is 0.25 g

            A.        21 g

            B.         3.4 g

            C.         0.21 g

            D.        0.34 g

20.       Which of the following chemical species is the oxidizing agent in the reaction below?

Cu (s) + 4 HNO₃ (aq) → Cu(NO₃)₂ (aq) + 2 NO₂ (g) + 2 H₂O (l)

A.       Cu (s)

B.        HNO₃ (aq)

C.        Cu(NO₃)₂ (aq)

D.       NO₂ (g)

An unknown amount of riboflavin (100 tablets) was dissolved in 1 liter of water, one milliliter of the solution obtained was diluted to one liter. The measured fluorescence of the resulting solution was 42 units. A pattern containing 9.05 mg / liter of riboflavin gave a reading of 32 units. What is the average amount of milligrams of riboflavin in each tablet?

The equilibrium constants of the reactions

FeO(s) + CO(g) = Fe(s) + CO2; K1

FeO (s) + H2(g) = Fe(s) + H2O (g) ; K2

temp (oC) 600 700 800 900 1000

-------------------------------------------------------------

K1 0.900 0.673 0.535 0.453 0.396

K2 0.332 0.422 0.499 0.594 0.668

Calculate the equilibrium constant of the reaction

CO(g) + H2O(g) = CO2 (g) + H2(g)

at the above temperature Also calculate the heat of the reaction.

Are the following compounds acidic, basic, or neutral?

1. barium nitrate

2. sodium chloride

3. potassium nitrite

4. iron III chloride

5. sucrose

6. magnesium carbonate

7. lithium sulfite

8. naphthalene

9. potassium permanganate

10. lead II chloride

11. copper II bromide

12. calcium sulfate

1. Answer any three of the following parts (a) - (d). (a) The hydrolysis of a compound A-B in a dilute aqueous solution proceeds in one elementary step: A-B + H2O → A-OH + H-B (i) Describe the order of this reaction. (ii) Outline the differential and the integrated rate laws for this reaction. (iii) Calculate the reaction rate constant if the concentration of A-B at time 10 s was 0.1 mol L-1 and at time 1000 s was 0.001 mol L-1 .