## A common shorthand way to represent a voltaic cell is

A common shorthand way to represent a voltaic cell is anode| anode solution || cathode solution |cathode A double vertical line represents a salt bridge or a porous barrier. A single vertical line represents a change in phase, such as from solid to solution.

(a) Write the half-reactions and overall cell reaction represented by Fe| Fe2+||Ag+ | Ag; sketch the cell.

(b) Write the half-reactions and overall cell reaction represented by Zn| Zn2+||H+ |H2; sketch the cell.

(c) Using the notation just described, represent a cell based on the following reaction:

ClO3(aq) + 3Cu(s) + 6H+(aq) → Cl(aq) + 3Cu2+ (aq) + 3H2O(I)

Pt is used as an inert electrode in contact with the ClO3 and Cl. Sketch the cell.

## Li-ion batteries used in automobiles typically use a LiMn2O4 cathode

Li-ion batteries used in automobiles typically use a LiMn2O4 cathode in place of the LiCoO2 cathode found in most Li-ion
batteries.

(a) Calculate the mass percent lithium in each electrode material?

(b) Which material has a higher percentage of lithium? Does this help to explain why batteries made with LiMn2O4 cathodes deliver less power on discharging?

(c) In a battery that uses a LiCoO2 cathode approximately 50% of the lithium migrates from the cathode to the anode on charging.

In a battery that uses a LiMn2O4 cathode what fraction of the lithium in LiMn2O4 would need to migrate out of the cathode to deliver the same amount of lithium to the graphite anode?

## Complete and balance the following equations, and identify the oxidizing

Complete and balance the following equations, and identify the oxidizing and reducing agents:

(a) Cr2O72-(aq) + I(aq) → Cr3+(aq) + IO3 (aq) (acidic solution)

(b) MnO4– (aq) + CH3OH(aq)  → Mn2+(aq)  + HCO2H(aq)  (acidic solution)

(c) I2(s) + OCl(aq)  → IO3– (aq) + Cl(aq)  (acidic solution)

(d) As2O3(s) + NO3(aq)  → H3AsO4(aq)  + N2O3(aq)  (acidic solution)

(e) MnO4(aq)  + Br(aq)  → MnO2(s) + BrO3(aq)  (basic solution)

(f) Pb(OH)42-(aq)  + ClO(aq)  → PbO2(s) + Cl(aq)  (basic solution)

## In some applications nickel–cadmium batteries have been replaced by nickel–zinc

In some applications nickel–cadmium batteries have been replaced by nickel–zinc batteries. The overall cell reaction for this relatively new battery is:

2H2O(I) + 2NiO(OH)(s) + Zn(s) → 2Ni(OH)2(s) + Zn(OH)2(s)

(a) What is the cathode half-reaction?

(b) What is the anode half-reaction?

(c) A single nickel–cadmium cell has a voltage of 1.30 V. Based on the difference in the standard reduction potentials of Cd2+ and Zn2+, what voltage would you estimate a nickel–zinc battery will produce?

(d) Would you expect the specific energy density of a nickel–zinc battery to be higher or lower than that of a nickel–cadmium battery?

## It was estimated that the eruption of the Mount Pinatubo

It was estimated that the eruption of the Mount Pinatubo volcano resulted in the injection of 20 million metric tons of SO2 into the atmosphere. Most of this SO2 underwent oxidation to SO3, which reacts with atmospheric water to form an aerosol.

(a) Write chemical equations for the processes leading to formation of the aerosol.

(b) The aerosols caused a 0.590.6°C drop in surface temperature in the northern hemisphere. What is the mechanism by which this occurs?

(c) The sulfate aerosols, as they are called, also cause loss of ozone from the stratosphere. How might this occur?

## In 2010, a team of scientists from Russia and the

In 2010, a team of scientists from Russia and the U.S. reported creation of the first atom of element 117, which is not yet named and is denoted [117]. The synthesis involved the collision of a target of 24997Bk with accelerated ions of an isotope which we will denote Q. The product atom, which we will call Z, immediately releases neutrons and forms 294117[117] :

24997Bk + Q → Z → 294117[117] + 310n

(a) What are the identities of isotopes Q and Z?

(b) Isotope Q is unusual in that it is very long-lived (its half-life is on the order of 1019 yr) in spite of having an unfavorable neutron-to-proton ratio (Figure 21.2). Can you propose a reason for its unusual stability?

(c) Collision of ions of isotope Q with a target was also used to produce the first atoms of livermorium, Lv. The initial product of this collision was 296116Lv. What was the target isotope with which Q collided in this experiment?

## Naturally found uranium consists of 99.274% 238U, 0.720% 235U, and

Naturally found uranium consists of 99.274% 238U, 0.720% 235U, and 0.006% 233U. As we have seen, 235U is the isotope that can undergo a nuclear chain reaction. Most of the 235U used in the first atomic bomb was obtained by gaseous diffusion of uranium hexafluoride, UF6(g).

(a) What is the mass of UF6 in a 30.0-L vessel of UF6 at a pressure of 695 torr at 350 K?

(b) What is the mass of 235U in the sample described in part (a)?

(c) Now suppose that the UF6 is diffused through a porous barrier and that the change in the ratio of 238U and 235U in the diffused gas can be described by Equation 10.23. What is the mass of 235U in a sample of the diffused gas analogous to that in part (a)?

(d) After one more cycle of gaseous diffusion, what is the percentage of 235UF6 in the sample?

## For the molecules shown in 24.85,Data from 24.85Identify each of

For the molecules shown in 24.85,

Data from 24.85

Identify each of the functional groups in these molecules:

(a)

(Responsible for the odor of cucumbers)

(b)

(Quinine — an antimalarial drug)

(c)

(Indigo — a blue dye)

(d)

(Acetaminophen — aka Tylenol)

(a) Which one(s) of them, if any, would produce a basic solution if dissolved in water?

(b) Which one(s) of them, if any, would produce an acidic solution if dissolved in water?

(c) Which of them is the most water-soluble?