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Math Snap
PROBLEM
Attempt All Questions 1. Dichromate ion (Cr2O72−) in acidic solution is a good oxidizing agent. Which of the following oxidations can be accomplished with dichromate ion in acidic solution? Explain a. Sn2+(aq) to Sn4+(aq) b. Ag(s) to Ag+(aq) 2. For each of the following cell diagrams a. Pt(s)Fe2+(aq),Fe3+(aq)∥Ag+(aq)Ag(s) b. Pt(s)Mn2+(aq),MnO4−(aq)Cu2+(aq)Cu(s) i. calculate the Ecell o ii. what is the change in Gibbs free energy? iii. is the cell reaction spontaneous or nonspontaneous? Explain. 3. Will the following reaction Cr2O72⋅(aq)+14H++6Ag(s)⟶2Cr3+(aq)+6Ag+(aq)+7H2O(l)Ecell =−0.023Vbe spontaneous if [Cr2O72−]=[Ag+]=0.675M,[Cr3+]=0.6M and pH=2 ? Explain. 4. Define the following terms a) Oxidation b) Oxidizing agent c) Salt bridge d) Liquid junction e) Standard electrode potential
STEP 1
1. The dichromate ion Cr2O72− is a strong oxidizing agent in acidic solutions. 2. Standard electrode potentials (E∘) are available for the relevant half-reactions. 3. Gibbs free energy change (ΔG) can be calculated using the formula ΔG=−nFEcello. 4. The Nernst equation can be used to determine cell potential under non-standard conditions. 5. Definitions are based on standard chemistry terminology.
STEP 2
1. Analyze the oxidation reactions with dichromate ion. 2. Calculate Ecello for given cell diagrams. 3. Determine Gibbs free energy change and spontaneity. 4. Evaluate the spontaneity of the given reaction under specified conditions. 5. Define the given chemistry terms.
STEP 3
Analyze the oxidation reactions with dichromate ion: a. Check if Sn2+(aq) can be oxidized to Sn4+(aq) using dichromate ion. - The standard reduction potential for Sn4+/Sn2+ is E∘=+0.15V. - The standard reduction potential for Cr2O72−/Cr3+ is E∘=+1.33V. - Since E∘ for dichromate is higher, it can oxidize Sn2+. b. Check if Ag(s) can be oxidized to Ag+(aq). - The standard reduction potential for Ag+/Ag is E∘=+0.80V. - Since E∘ for dichromate is higher, it can oxidize Ag.
STEP 4
Calculate Ecello for given cell diagrams: a. For Pt(s)Fe2+(aq),Fe3+(aq)∥Ag+(aq)Ag(s): - Ered∘(Fe3+/Fe2+)=+0.77V - Ered∘(Ag+/Ag)=+0.80V - Ecello=Ecathode∘−Eanode∘=0.80V−0.77V=0.03V b. For Pt(s)Mn2+(aq),MnO4−(aq)Cu2+(aq)Cu(s): - Ered∘(MnO4−/Mn2+)=+1.51V - Ered∘(Cu2+/Cu)=+0.34V - Ecello=0.34V−1.51V=−1.17V
STEP 5
Determine Gibbs free energy change and spontaneity: a. For cell diagram (a): - ΔG=−nFEcello - n=1 (for Fe3+/Fe2+ and Ag+/Ag) - ΔG=−(1)(96485C/mol)(0.03V)=−2894.55J/mol - Reaction is spontaneous as ΔG<0. b. For cell diagram (b): - ΔG=−(2)(96485C/mol)(−1.17V)=226,902.3J/mol - Reaction is nonspontaneous as ΔG>0.
STEP 6
Evaluate the spontaneity of the given reaction under specified conditions: - Use the Nernst equation to find Ecell under non-standard conditions. - Ecell=Ecell∘−nFRTlnQ - Q=[Cr2O72−][H+]14[Cr3+]2[Ag+]6 - Substitute values: Q=(0.675)(10−2)14(0.6)2(0.675)6 - Calculate Ecell and determine if the reaction is spontaneous (Ecell>0).
SOLUTION
Define the given chemistry terms: a) Oxidation: The process of losing electrons in a chemical reaction. b) Oxidizing agent: A substance that gains electrons and is reduced in a chemical reaction. c) Salt bridge: A device used in an electrochemical cell to maintain electrical neutrality by allowing the flow of ions. d) Liquid junction: A boundary between two different electrolyte solutions in an electrochemical cell. e) Standard electrode potential: The measure of the individual potential of a reversible electrode at standard state, which is 1M concentration, 1atm pressure, and 25∘C.