Extra Credit 34

S17.5.2

When selecting a battery for a new application, one should consider the mass of the battery (how heavy/light it is), the toxic components of the battery (what chemicals and how to dispose of them properly), the ability to withstand certain heat and pressure, the price of the battery, and the potential (how much energy it has and how long it will last).

S12.2.1

The collision theory states that increasing the concentration of a reactant increases the number of collisions and therefore, increases the reaction rate. Temperature is directly proportional to the kinetic energy of particles and therefore, if temperature increases, the average kinetic energy will increase. This will result in an increase of the frequency and intensity of collision, and thus increases the rate of reaction. Increasing the surface area will result in more collisions and thus increases the reaction rate. Therefore, if the magnesium atoms are split into smaller pieces as opposed to forming one big piece, there will be more surface area for the reaction between magnesium and hydrochloric acid to occur.

S12.5.6

An increase in temperature affect the rate of reaction because when temperature is increased, molecular velocity will increase and there will be an increase in particles colliding with each other. The increase in molecular velocity due to the increase in temperature will cause an increase in the frequency of the collisions. This in turns will cause the rate of reaction to increase.

S21.4.1

The types of radiation emitted by the nuclei of radioactive elements are:

a. alpha radiation: occurs when an alpha particle (consisting of two protons and two neutrons) is given off

b. beta radiation: can be either an electron or a positron (particle with the same size and mass as an electron but has a positive charge)

c. gamma radiation: consists of a photon of energy emitted from an unstable nucleus; has no mass and no charge

d. neutrons radiation: occurs when a neutron is emitted from the nucleus of an atom; has mass but no charge

S20.4.24

Reduction half reaction: \(\ce{Ag^+}(aq)+\ce{e^-}⟶\ce{Ag}(s)\) E^o=+0.800V

Oxidation half reaction: \(\ce{2H^+}(aq)+\ce{e^-}⟶\ce{H2}(s)\) E^o=0V

Ag is the only species that is reduced and only H₂ is oxidized. Cl remains in the oxidation state of -1 throughout the reaction. Since it doesn't change, Cl doesn't contribute to the cell potential.

Since E^o_cell = E^o_cathode - E^o_anode

E^o_cell = 0.800V - 0V

E^o_cell = +0.800V

Therefore, this plan will work because the two half reaction has a cell potential of +0.800V. Since it's a positive number, this means that the reaction will be spontaneous.

S20.2.5

Lithium would have the greatest tendency to be oxidized because lithium has the lowest reduction potential in the electrochemical series (E^o=-3.05V) as opposed to zinc (E^o=-1.66V) and sulfur (E^o=+0.14V). Therefore, lithium would be a better reducing agent and have the greatest tendency to be oxidized.

S20.9.9

\(\ce{Pb^2+}(aq)+\ce{2e^-} = \ce{Pb}(s)\) \(\ce{E^0} = -0.13V\)

This means that 2 moles of e^- transferred is 1 mol of Pb reduced.

n_e = \(\frac{It}{F}\)

n_e = \[\frac{5.0A\times {2.0}h\times {60}min/hr\times {60}sec/min}{9.65\times {10^4} c/mol} = 0.373 \ mol \ e^- \ transferred\]

n_e = \(\ce0.373 \ mol \ e^- \ transferred\)

\(\ce0.373 \ mol \ e^- \ transferred\times \frac{1\ mol\ Pb}{2\ mol \ e^-} = 0.187 \ mol \ Pb\)

\(\ce0.187 \ mol \ Pb\times {207.2 \ g/mol} = 38.65 \ g \ Pb \ reduced\)

S14.6.7

The slowest step will be the rate determining step. The intermediate shows up as a product of one step and canceled out as a reactant of the next step.

Second order: Rate =−k[A][B]

Determined: \(\ce{NO2}+\ce{NO2}→\ce{NO3}+\ce{NO}\)

\(\ce{NO3}+\ce{CO}→\ce{NO2}+\ce{CO2}\)

Therefore, the slow step is first step because the low temperature leads to less collisions, which means a slower rate. And because of the lower temperature, it doesn’t reach the required activation energy of the second step and so the second step cannot be done.