Solubility Product
Explain the difference between solubility and solubility-product constant.
Solubility is the molar concentration of the compound in a saturated solution. Solubility-product constant is the equilibrium constant for the equilibrium between an undissolved salt and its ions in a saturated solution.
a) What is a galvanic (or voltaic cell)?
b) What is an electrolytic cell?
a) A galvanic cell is an electrochemical cell in which a spontaneous chemical reaction is used to generate electric current.
b) An electrolytic cell is an electrochemical cell in which an electric current is used to drive a non-spontaneous reaction.
a) Which is the strongest oxidizing agent?
b) Which is the strongest reducing agent?
a) F2(g).
b) Li(s).
a) Define the term "reaction rate".
b) What is the instantaneous rate?
a) Reaction rate is the change of the concentration of products or reactants over time.
b) The instantaneous rate is the slope of the line drawn tangent to the concentration vs time curve at a specific time.
a) What is a reaction mechanism?
b) What is meant by the term elementary reaction?
a) A reaction mechanism is a series of elementary reactions that describe how the overall reaction occurs and explain the experimentally determined rate law.
b) An elementary reaction is a process that occurs in a single event.
If AgNO3(aq) is added to a saturated solution of AgOH(s), what will happen to the solubility of AgOH(s)? Explain why.
Decrease, because of common ion effect.
a) What are the oxidation states of all species in the following redox reaction?
b) Which species is being oxidized and which is being reduced?
a) Zn(s) = 0; H2(g) = 0; H+ = +1; Zn2+ = +2
b) Zn(s) is being oxidized (reducing agent); H+ is being reducing (oxidizing agent)
a) What conditions must be met for a reduction potential to be a standard reduction potential?
b) What is the standard reduction potential of a standard hydrogen electrode?
c) Why is impossible to measure the standard reduction potential of a single half-reaction?
a) Substances should be in standard conditions, meaning gases at 1 bar pressure and aqueous solution at 1 M concentration.
b) Standard potential of hydrogen electrode is 0.0 V.
c) Only the difference between two electrode potentials can be measured.
a) What are the four factors that can affect the rate of a chemical reaction?
b) Which of the above four factors affect the rate constant?
a) concentration of reactants, surface area of reactants, temperature, and presence of a catalyst.
b) Only temperature.
a) What factors determine whether a collision between two molecules will lead to a chemical reaction?
b) What is activation energy?
a) - The energy of collision (Emin)
- Collision frequency (A)
- Orientation of the molecules
b) The activation energy is the minimum kinetic energy required for the collision to result in a reaction.
If HNO3(aq) is added to a saturated solution of AgOH(s), what will happen to the solubility of AgOH(s)? Explain why.
Increase, because of removal of OH- ions due to the formation of water, a weak electrolyte:
H+ + OH- -> H2O
Here is the cell diagram:
Pb(s) | Pb2+(aq) || Sn2+(aq) | Sn(s)
a) What are the two relevant electrodes in this galvanic cell?
b) Where does oxidation and reduction take place?
c) What is the overall redox reaction?
a) Pb(s)-Anode and Sn(s)-Cathode.
b) Oxidation occurs at the anode, reduction occurs at the cathode.
c) Pb(s) + Sn2+(aq) --> Pb2+(aq) + Sn(s)
Are the Eocell and ΔGo values positive, negative or zero when
a) K<1
b) K=1
c) K>1
Since ΔGo = -nFEocell and ΔGo = -RT ln K, then
Eocell = (RT/nF) ln K
a) Eocell <0; ΔGo >0
b) Eocell =0; ΔGo =0
c) Eocell >0; ΔGo <0
How do the half-lives of a) first-order and b) second-order reactions differ?
a) For first order reactions, the half-life depends solely on the reaction rate constant, k.
b) For second order reactions, the half-life depends on both the initial concentration, C0, and the rate constant, k.
a) Define an intermediate.
b) What is a catalyst?
a) An intermediate is produced in one elementary step and is consumed in a later elementary step of the reaction and therefore does not appear in the overall equation.
b) A catalyst is a substance that increases the rate of the reaction by lowering the activation energy (Ea). The catalyst appears in the first and last elementary steps of the reaction, but does not appear in the overall equation.
If NH3(aq) is added to a saturated solution of AgBrO3(s), what will happen to the solubility of AgBrO3(s)? Explain why.
Increase, because of removal of Ag+ ions due to the formation of the complex:
Ag+ + 2 NH3 -> Ag(NH3)2+
From the standard reduction potential table we have received the following information:
Eo(NO3-/NO(g)) = +0.96 V
Eo(Ag+/Ag(s)) = +0.80 V
Eo(Cr2O72-/Cr3+) = +1.33 V
Rank the above ions in order of increasing strength as oxidizing agents?
Ag+ < NO3- < Cr2O72-
a) A galvanic cell is constructed with all reactants and products in their standard states. Will the concentrations of the reactants increase, decrease, or remain the same as the cell operates?
b) What happens to the emf of a cell if the concentrations of the products are increased?
a) Decrease. As the spontaneous chemical reaction of galvanic cell proceeds, the concentrations of products increase and the concentrations of reactants decrease.
b) If concentrations of products increases, Q increases, so based on Nernst equation (E = Eo -RT/nF lnQ) the emf, E, decreases.
For the following reaction: A + B ---> C it is seen that when [A] doubles the initial rate quadruples; and when both [A] and [B] double, the initial rate quadruples.
a) What are the orders with respect to A and B?
b) What is the overall order of the reaction?
a) 2nd order with respect to A; 0th order with respect to B.
b) overall 2nd order.
What is the activation energy of a reaction in which the rate constant increases by a factor of 2, when the temperature increases from 290 K to 300 K.
ln(k1/k2) = Ea/R (1/T2 - 1/T1)
Ea = 50 kJ/mol
a) Write the Ksp expression for Sr3(PO4)2 (s);
b) What is its value, if solubility of the salt is 10-2M?
a) Ksp=[Sr2+]3[PO43-]2
b) Ksp=(3s)3(2s)2 = (27s3)(4s2)=108s5 = 108(10-2)5=
1.08 x 10-8
Here is the cell diagram:
Ca(s) | Ca2+(aq) || Mn2+(aq) | Mn(s)
a) Calculate the standard cell potential of the above cell knowing that Eo(cathode) = -1.17 V and Eo(anode)= - 2.87 V.
b) What can you say about ΔG and spontaneity?
a) Eo(cell)= Eo(cathode) - Eo(anode)= (-1.17) - (-2.87) = 1.70 V
b)ΔGo = -nFEo. Since Eo >0 then ΔGo < 0 ; therefore rxn. is spontaneous
a) If the electrolysis of NaCl (molten) is happening, what are the products produced at the anode and at the cathode?
b) If the electrolysis of NaCl (aq) is happening, are the products produced at the anode and at the cathode the same as above or not? And why?
a) Cl2(g) at the anode and Na(l) at the cathode
b) The products produced at the electrodes are different, because the oxidation half-reaction of H2O and reduction half-reaction of H2O need to be taken into account. The products will be: O2(g) at the anode; H2(g) at the cathode.
For the reaction CV+ + OH- ---> CVOH the absorbances of the solution mixture were collected over time using a Vernier spectrometer. By graphing the data it was found that the line of [CV] as a function of time has an R2= 0.889; the line of Ln[CV] as function of time has an R2= 0.987; and the line of 1/[CV] as a function of time has an R2= 0.955.
a) What is the order with respect to CV+?
b) It was found that when [OH-] doubled, the rate constant, found by the slope of the best-fit line, doubled. What is the order with respect to OH-?
c) What is the overall order of the reaction?
a) 1st order with respect to CV+;
b) 1st order with respect to OH-;
c) 2nd order overall.
The reaction 2 NO (g) + Cl2 (g) ----> 2 NOCl (g) was performed under conditions of constant [Cl2]. After processing the data, it was found that the graph of 1/[NO] as a function of time was linear with an R2 = 0.999.
a) What is the order with respect to NO?
b) It was found that when [Cl2] doubled, the rate constant, found by the slope of the best-fit line, doubled. What is the order with respect to Cl2?
c) Is the following mechanism consistent with the experimental rate law?
a) 2nd order with respect to NO.
b) 1st order with respect to Cl2.
c) Yes, the two-step mechanism is consistent with the experimental rate law, assuming that the second step is the rate determining step. It is 2nd order with respect to NO and 1st order with respect to Cl2.