105B Lab Exam

Rate=k[A]ⁿ[B]^m

Reactions take place because of collisions between reactant particles with proper orientation and with at least the minimum amount of energy (activation energy, A_e).

Temperature is the measure of the average kinetic energy of particles. 

To determine the effect of initial reaction concentration and temperature on the rate of the reaction.

H₂O₂, and DI water. KI was held constant.

Volume of oxygen gas produced (molarity) / Volume of solution was graphed, and the rate of reaction was equivalent to the slope of the line.

It increases reaction rate

It increases reaction rate

Determine the order of the reaction by using Beer’s law and integrated rate laws on the absorbance vs time data.

[A]_t Vs t

ln[A]_t Vs t

1/[A]_t Vs t

The “pseudo” rate constant in this case was utilized when we were unable to use the integrated rate law equations because we had two reactants rather than one. So, the sodium hypochlorite (NaOCl) was applied in excess to remain essentially constant throughout the reaction as the Blue #1 concentration changed.

To understand how the addition of reactants or products, change in pH or change in temperature affects the equilibrium position of a chemical reaction.

If stress is imposed on a system at equilibrium, the equilibrium concentration of reactants and products will shift in such a manner as to relieve the stress. 

To determine concentrations of HB and B_^- of BTB and H₃O⁺ using spectroscopy and pH measurements, and using those concentrations to calculate the K_In (indicator).

BTB is yellow in acidic conditions and blue in basic conditions.

432nm

616 nm

To practice making buffer solutions of desired pH and analyzing how the capacity of a buffer solution depends both on pH and the absolute concentrations of the conjugate acid-base pair.

when a buffer solution is no longer resistant to pH changes.

1. Prepare the solution using a known volume and molar concentration of the weak acid, acetic acid. Add an appropriate amount of moles of the conjugate base, aqueous sodium acetate, to achieve the correct ratio of acid and conjugate base.

2. Prepare the solution using a known volume and molar concentration of the weak acid, acetic acid. Add an appropriate amount of strong base, sodium hydroxide, to get the correct ratio of acid and conjugate base.

To experimentally determine the K_a for weak acids by studying the pH at different parts of a titration curve.

using an electronic instrument (pH meter) to measure the difference in electric potential to determine pH.

An acid that dissociates in a stepwise manner 3 times, meaning an acid with 3 equivalence points in a titration.

basic

To calculate the solubility product, gibbs free energy, change in enthalpy and change in entropy of calcium and hydroxide ions to observe how temperature affects solubility.

only at high temperatures

always spontaneous

never spontaneous

only at low temperatures

Read and understand line notation, calculate cell potential, understand oxidation-reduction reactions and how an electrolytic cell functions.

to neutralize the flow of electrons and keep. a constant charge

different substances in different states

different substances in the same state

the anode and cathode; the double line represents the salt bridge

1. Electrochemical reactions of metals: combined solid metals and ionic metal solutions to observe electrochemical reactions.

2. Galvanic cells: galvanic cells made w/ 6 different combinations of metals to observe the strength of the cell (in voltage)

3. Electrolytic cells: 2 solid copper pieces forming an electrolytic cell and weighing after 20 minute interval to observe exchange of electrons (in grams).

Correctly set up galvanic cells and accurately measure change in mass to distinguish between cathode and anode systems and detect flow of electrons using voltage. 

 an undesired electrochemical reaction that occurs when an electrochemical cell naturally forms with a metal and a second chemical in the environment (oxygen).

two different metal types are in electrical contact with one another. More active metal (greater reduction potential) will undergo corrosion more rapidly, and the metal with the more positive reduction potential will undergo corrosion more slowly.

The crystal lattice of iron becomes strained when the metal is cold worked or shaped. The atoms in the most severely distorted crystal lattice become more anodic and so they corrode more rapidly than other parts of the metal. 

Oxygen is present at higher concentrations at the surface of the water so it pulls electrons from the hull at the surface. Parts of the ship that are below the water level are exposed to a lower concentration of oxygen and thus replace the electrons at the surface. This makes the metal below the surface the anode and the metal at the surface the cathode. The oxidation that occurs at the anode dissociates the solid iron into cationic aqueous iron, damaging the ship.

When corrosion is controlled by using an external current to connect the metal to a more easily corroded metal, protecting the desired metal by making it the cathode and sacrificing the other metal to be the anode.

Observe the light spectrum of octahedral complexes and apply knowledge of crystal field theory to determine the spectrochemical series of multiple solutions.

a theory that explains the bonding between a transition metal ion and its ligands by considering the ligands to be negative point-charges arranged in a specific geometry around the central transition metal ion.

X²-y² and z² orbitals are highest in energy because they point directly toward the ligands.

Xy, yz, xz orbitals are lower in energy because they interact less directly with the ligands.

z²

x²-y²

xy

yz

xz