Thermodynamics
Give the definition of entropy
Disorder/randomness of a system
What is the main difference between Galvanic and electrolytic cells? (2 correct answers)
Polarity of electrodes and spontaneity of reaction
Given the following balanced equation for a redox reaction:
3MnO2(s) + 12H+(aq) + 2Fe(s) → 3Mn2+(aq) + 6H2O + 2Fe3+(aq)
Determine the value of n for this reaction, i.e. the number of electrons transferred.
6
Give the three amphoteric oxides (that you are required to know)
ZnO, BeO, Al2O3
What is the densest element?
Osmium
In thermodynamics, we are interested in the direction of reaction, L→R or R→L, and also in the relative
amounts of left- and right-side species at equilibrium. Which one of the following statements is correct?
A) If Q is less than K, the reaction proceeds in the right-to-left direction.
B) If ΔHo > 0 and ΔSo < 0, then the reaction definitely proceeds in the right-to-left direction
C) If K is much smaller than 1, then the concentrations of right-hand side species are very small at equilibrium.
D) If K is much larger than 1, then the reagents on the left side are completely consumed.
E) The direction of reaction cannot be determined from the value, including sign, of ΔG alone.
C
What mass of Cr(s) (Molar mass 52.00g/mol) will be deposited at the cathode of an electrolytic cell when a current of 38.6 Amp is passed for 35.0 minutes through a cell containing CrCl3(aq)?
14.6 g
Determine the oxidation states of nitrogen in NH3 and KNO2.
-3, +3
Which is the correct set of acid-base assignments for the given oxides?
ZnO NO2 K2O
A) Basic Basic Acidic
B) Acidic Neutral Amphoteric
C) Neutral Acidic Basic
D) Basic Neutral Amphoteric
E) Amphoteric Acidic Basic
E
How many elements are found in a typical phone?
up to 75!
Which of the following statements concerning ΔGo is/are correct?
1. The reaction: 2NaCl(l) → 2Na(l) + Cl2(g) occurs in an electrolytic cell (That is true). Therefore it is known that ΔGo < 0 for this reaction.
2. NH4Cl(s) dissolves readily in water, with a decrease in temperature of the water (That is true). Therefore it is known that ΔG< 0 for this process.
3. HCN is a weak acid (that is true). Therefore it is known that ΔGo > 0 for the reaction:
HCN(aq) + H2O ↔ H3O+(aq) + CN-(aq).
2 and 3
Given the half-reactions:
Cl2(g) + 2e- → 2Cl-(aq) Eored = +1.36V
Fe3+(aq) + e- → Fe2+(aq) Eored = +0.77V
Determine the voltage, E cell, generated by the spontaneous reaction between Cl2(g) and Fe2+(aq).
-0.59V
Which element has the highest reduction potential? Why?
F2, electronegativity
Which one of statements (A) – (D) concerning the halogens is NOT correct? If all are correct, select (E).
A) Fluorine and chlorine have large positive electronegativities
B) The acid strength of the oxyacids of chlorine increases with increasing oxidation state of the chlorine
C) Elemental fluorine is made by electrolytic oxidation of a suitable compound of fluorine in the absence of water.
D) Elemental chlorine is a stronger oxidizing agent than elemental bromine
E) Statements (A) – (D) are all correct.
E
What element is the most common termination point of radioactive decay?
Lead
Ca(OH)2(s) ↔ Ca2+(aq) + 2OH-(aq), ΔGo = +30.10kJ at 298K. Determine the value of ΔG in kJ (non-standard conditions) when [Ca2+] = 2.60 x 10-4M and [OH-] = 6.20 x 10-2M at this temperature.
-4.10kJ
Which one of the following definitions is NOT correct?
A) For a system under standard conditions, the partial pressure of each gas is 1atm, the concentration of each dissolved species is 1M; standard conditions can occur at any temperature.
B) In a Galvanic cell, a spontaneous redox reaction generates electrical voltage and current.
C) Hydration of an ion is defined as the reaction of the ion with water to form an acidic or basic solution.
D) The cathode of an electrochemical cell is defined as the electrode to which cations drift during operation of the cell.
E) Reduction is defined as gain of one or more electrons by a species.
D
Balance this reaction:
P4O10 + H2O -->
P4O10 + 6 H2O --> 4 H3PO4
Which one statement concerning the properties of oxygen (O) and sulfur (S) is NOT correct?
A) In compounds, S often adopts a positive oxidation state but O rarely does so.
B) O has a higher electronegativity than S
C) Oxygen is found in nature in the elemental form, but sulfur is found in nature only in compounds, such as S2O3 and H2S.
D) Elemental oxygen has the molecular formula O2, containing a double bond, whereas elemental sulfur has the formula S8, containing only single bonds.
E) Both O and S are found in both acidic and basic compounds or ions.
C
Which of the following is known as laughing gas and which one can kill you within 1 hour of exposure?
N2O NO2
N2O is laughing gas and NO2 is toxic!
For a reaction at 75 C, it is known that ΔSo = -135 J/K and its equilibrium constant, K, is 7.50 x 103.
Determine the value of ΔH in kJ for this reaction.
-72.8kJ
Henry wanted to study the reduction of Fe3+ ion to Fe2+ ion in a Galvanic cell under standard conditions.
Which is a correct set of chemicals to use in the appropriate half-cell of this Galvanic cell? Hint: NO3- is a spectator ion.
A) 1M Fe(NO3)2(aq) + 1M Fe(NO3)3(aq), with a Pt electrode
B) 1M Fe(NO3)3(aq) with an Fe(s) electrode
C) 1M Fe(NO3)2(aq) with a C (graphite) electrode
D) 0.5M Fe(NO3)2(aq) + 0.5M Fe(NO3)3(aq) with a Pt electrode
E) 1M Fe(NO3)2 (aq) + 1M Fe(NO3)3(aq), with an Fe(s) electrode
A
Given the following half-reaction:
Cr2O72-(aq) + 14H+(aq) + 6e- → 2Cr3+(aq) + 7H2O, Eored = +1.23V
Based on this half-reaction and Eo value, which one of (A) – (D) is correct?
A) Cr2O72-(aq) is a strong reducing agent
B) Cr3+(aq) cannot act as an oxidizing agent
C) Cr3+(aq) is a weak reducing agent
D) Cr2O72-(aq) is a strong oxidizing agent.
E) Two of the above are correct
F) More than two of the above are correct
F
Each of the following pairs of chemicals undergoes reaction. Which of the given classes of reaction
is/are completely correct?
Reactants Class of reaction
1. CO2(g) + H2O → Products Non-redox combination
2. Ca(s) + Br2(l) → Products Single displacement: redox
3. HNO2(aq) + OH-(aq) ↔ Products Bronsted-Lowry H+ transfer: non-redox
1 and 3
Phosphorus coordinates to which metal to form bones and teeth?
Calcium