An electrochemical cell is based on the following two half-reactions:
Ox: Pb(s)?Pb2+(aq, 0.21M )+2e?
Red: MnO?4(aq, 1.25M )+4H+(aq, 2.5M )+3e??
MnO2(s)+2H2O(l). Compute the cell potential at 25 ?C.

Due to its hardness, thermal stability, and resistance to wear, silicon nitride is used in cutting tools. It can be produced through the following chemical reaction. 3 Si(s) + 2 N2(g) „³ Si3N4(s) A combination of 123 g of N2 and 160 g Si is used.

a. What is the theoretical yield of silicon nitride?

b. What mass of the excess reactant remains after the reaction is allowed to progress?

Part 2 – Comparing the reactivity of some metals with acids Many metals react with acids, via an electron-transfer (oxidation-reduction) reaction that transforms the metal into dissolved metal ions. A co-product of this reaction is hydrogen gas, formed when hydrogen ions in the acid solution take up electrons from the metal and couple. Your task here is to test a few different metals to see how their reaction intensities compare. 1. Obtain 12 clean small test tubes (they can be slightly wet). Divide them into three sets of four tubes, and label the sets as: “HCl”, “acetic acid” and “water”. 2. To the four “water” test tubes, add about 1 mL of water. To the four “HCl” test tubes, add about 1 mL of 3 M hydrochloric acid using the 1 mL graduated pipette that goes with the reagent bottle. To the four “acetic acid” tubes, add 1 ml of 3 M acetic acid. (Do not mix up the droppers!) Carefully note the smells of the two acids. Do this by wafting air over the sample towards your nose with your hand - never smell a chemical directly. Exp.2: OBSERVATIONS 2 - 4 3. Now divide the tubes into four sets, one of each kind. Label them (or place them on a labeled sheet of paper) as: “steel wool”, “Mg”, “Al sheet” and “Al foil”. 4. To each “steel wool” tube: add a small loosely packed ball of steel wool about 3 mm in diameter. Make initial observations and note the time, then push the steel wool down into the liquids with a clean glass stir rod. Record your observations immediately after mixing and again as time passes: colour changes, gas formation, solid formation (cloudiness), odours, and heat evolution all provide evidence of chemical reaction. [Make notes on Observations/Data page.] Note: compare the acid-treated samples to the “control” water-treated sample – only then can you determine whether any chemical reactions observed are caused by the acid or simply by the water also present. 5. Repeat step 4 with the other metals: ~5 mm strip of magnesium ribbon, 5 mm square of aluminum sheet, and 5 mm diameter loose ball of aluminum kitchen foil.

Regarding Part 2: Consider the physical nature of the metals you tested, their positions on the periodic table, and the different strengths of the acids you used. What conclusions can you draw from your observations of the action of the acids on the different metals you tested? Be careful to explicitly distinguish between speculations you cannot back up and speculations based on any chemistry you may already have learned.

What are the major species present in a 0.150-M NH3 solution? Calculate the [OH2] and the pH of this solution.

The standard enthalpies of formation oxides of the fourth period eleemtns of the d block are as follows:

TiO VO MnO FeO CoO NiO CuO ZnO

-518 -431 -385 -264 -239 -241 -155 -348

a)write a general equation suitable for calculating the lattice energy of any of these oxides, based on theoritical data

b)Find the lattice energies of TiO, CuO, and ZnO

c) Overall the most dissimlar enthalpy values are those of TiO and CuO; the most dissimilar enthaly values of neighvoring oxides are those of CuO and ZnO. Which thermodynamic factor is apparently repsonsible for each of these dissimilarities? d)What factor of theoritcial lattice energy calculations is most repsonsible for substantial change in lattice eneregies between TiO and CuO?

How do enzymes increase rates of biochemical reactions?

What are the three classes of reversible inhibitors? Briefly describe them and their effects on apparent Km and Vmax.

The name of the experiment is Preparation of Synthetic Banana oil. The name of the author of the book is John Lehma. chapter 5.

(incase needed, we used 20.o mmol of isopentyl and 40 mmol of glacial acetic acid)

In the ''understanding experiment'' section, it was stated that the reaction of an equimolar mixture of isopentyl alcohol and acetic acid will produce, at most, 67% of the theoretical amount of isopentyl acetate. verify this with an equilibrium constant calculation, using K = 4.2 . b) compare this with the corresponding percentage for the conditions used in this experiment (see exercise 1 ) Please explain well.

Exercise 1 is also found in the book, however the ammount of chemicals used in the experiment are stated above. Thank you.

Air is heated from 25c to 150c . The flow rate of air at the exit of the heater is 1.25m^3/min and the air pressure is 122 Kpa absolut .

calculate the heat requirement in KW , assuming ideal gas behavior and that the kinetic & potential energy are negligible.

how will absorbing aerosol particles in the boundary layer affect air pollution buildup and cloud formation only if the effects of the aerosol particles on atmospheric stability are considered

what is the change in entropy, enthalpy and gibbs free energy when 1 L of ideal gas i, 3 L of ideal gas j and 4 L of ideal gas k, each at 1 atm and room temperature (298.15K) blend to form a gas mixture at the same conditions?

Calculate the molar solubility of Fe(OH)₂ in a buffer solution where the pH has been fixed at the indicated values. K_sp = 7.9 x 10^-16.

(a) pH 7.6
_________M
(b) pH 10.2
__________M
(c) pH 12.0
___________M

Calculate the pH change when 10. mL of 3.0 M HCl are added to 500. mL of the following

A ) pure water

B) aqueous solution of 3.0g of formic acid

C) aqueous solution of 4.0g potassium formate

D) aqueous solution containing 3.0 g of formic acid and 4.0 g of potassium formate

1. Briefly describe how a drying agent works. List the names and chemical formulas for five typical drying agents.

2. Elemental bromine (Br2)reacts with 3-hexene to form 3,4-dibromohexane.

a. Write out the balanced equation for this reaction.

b. If 11.5 g of 3-hexene is reacted with 8.8 g Br2, what is the theoretical yield of 3,4- dibromohexane?

c. If you did the reaction described in (c) and isolated 15.9 g of 3,4- dibromohexane, what is the percent yield for the reaction?

3. How can you tell, visually, when an organic liquid is dry after adding a drying agent?

4. Write out the mechanism for the dehydration of 2-butanol in the presence of sulfuric acid (via an E1 mechanism).

A 1L buffer solution is 0.150M in HC7H5O2 and 0.250M in LiC7H5O2. Calculate the pH of the soln after the additon of 100mL of 1.00M HCl. The Ka HC7H5O2 = 6.5x10^-5