【正文】 adiation, colorless dihydroazulene J undergoes photoinduced rearrangement to the corresponding vinylheptafulvene K. The vinylheptafulvene undergoes thermal reversion to dihydroazulene. C H3C NC Nh vh e a tN C C NC H3JK12345678910 For translation: aheat 第 25 頁(yè) 共 64 頁(yè) Country: Language: 37 Which pound will absorb light with longer wavelength? Select your answer from the following choices. (a) J (b) K 38 Compound K can react with one equivalent of CF3CO2H to generate a stable aromatic salt. Which position of K is most likely protonated? Select your answer from the following choices. (a) C2 (b) C3 (c) C4 (d) C5 第 26 頁(yè) 共 64 頁(yè) Country: Language: Problem 4: Gold Capital of Asia Total Score: 42 points A Chiufen, the old mining town located within the hills in the northeast Taiwan, is a place where you can really experience Taiwan39。s historical legacy. It was the site of one of the largest gold mines In Asia. Accordingly, Chiufen is often referred to as the Gold Capital of Asia. The pound KCN is traditionally used to extract gold from ore. Gold dissolves in cyanide (CN) solutions in the presence of air to form Au(CN)2, which is stable in aqueous solution. 4Au(s)+8CN－ (aq)+O2(g)+2H2O(l) 4Au(CN)2－ (aq)+4OH－ (aq) 4A1 Draw a structure for Au(CN)2175。 showing the spatial arrangements of the atoms. 4A2 How many grams of KCN are needed to extract 20 g of gold from ore? Show your work. Aqua regia, a 3:1 mixture (by volume) of concentrated hydrochloric acid and nitric acid, was developed by the alchemists as a means to ―dissolve‖ gold. The process is actually a redox reaction with the following simplified chemical equation: Au(s)+NO3－ (aq)+Cl－ (aq) AuCl4－ (aq)+NO2(g) 4A3 Write down the half reactions, and use them to obtain a balanced redox reaction for this process. 4A4 What are the oxidizing and reducing agents for 4A3 process? Country: Language: 4A1 4A2 4A3 4A4 4A5 4A6 4B1 4B2 4B3 4B4 4B5 Points 2 4 4 2 6 2 2 2 2 8 8 第 27 頁(yè) 共 64 頁(yè) Gold is too noble to react with nitric acid. However, gold does react with aqua regia because the plex ion AuCl4? forms. Consider the following halfreactions: Au3+(aq)+3e－ → Au(s) Eo=+ AuCl4－ (aq) +3e－ → Au(s)+4Cl － (aq) Eo=+ An electrochemical cell can be formed from these two redox couples. 4A5 Calculate the formation constant for AuCl4?at 25176。C: K = [AuCl4?] / [Au3+] [Cl?]4 4A6 The function of HCl is to provide Cl175。. What is the purpose of the Cl175。 for the above reaction. Select your answer from the following choices. (a) Cl175。 is an oxidizing agent (b) Cl175。 is a reducing agent (c) Cl175。 is a plexing agent (d) Cl175。 is a catalyst B Gold Nanoparticles The synthesis and characterization of gold nanoparticles is currently an active research area. The BrustSchiffrin method for the synthesis of gold nanoparticle (AuNP) allows the facile preparation of thermally stable and airstable AuNPs of reduced polydispersity with a controlled size distribution ranging in diameter between and nm. The preparative procedure is briefly described as follows. An aqueous solution of HAuCl4 is mixed with a toluene solution of tetranoctylammonium bromide. The solution is mixed with dodecahiol and is treated with an excess of of the AuNPs is evidenced by the immediate, pronounced darkening of the toluene ca. 24 h, the toluene solvent is removed with a rotary evaporator and the resulting solid washed on a frit with ethanol and hexane to remove excess thiol. These AuNPs can be repeatedly isolated and redissolved in mon anic solvents without irreversible aggregation or deposition. 4B1 Is the methodology for this fabrication referred to a topdown or a bottomup approach? Select your answer from the following choices. (a) topdown approach, which entails reducing the size of the smallest structures to the nanoscale (b) bottomup approach, which involves manipulating individual atoms and molecules into nanostructures 第 28 頁(yè) 共 64 頁(yè) Country: Language: 4B2 The trimethylnoctylammonium bromide can also be used as a phasetransfer reagent. It can carry AuCl4175。 from an aqueous phase to an anic phase. Which property does trimethylnoctylammonium bromide possess to function as an efficient phasetransfer reagent? Select your answer from the following choices. (a) one side of the molecule is electropositive, the other side is electronegative. (b) one side of the molecule is hydrophilic, the other side is hydrophobic. (c) one side of the molecule is acidic, the other side is basic. 4B3 What is the function of NaBH4 in this preparation? Select your answer from the following choices. (a) reducing agent (b) oxidizing agent (c) neutralization agent (d) plexing agent 4B4 If the average diameter of a gold nanoparticle is 3 nm, what is the estimated number of Au atoms in each nanoparticle? (the atomic radius of Au is nm). Select your answer from the following choices and show your work. (a) 102 (b) 103 (c) 104 (d) 105 4B5 What is the estimated percentage of Au atoms on the surface of a nanoparticle? Select your answer from the following choices and show your work. (a) 2030% (b) 4050% (c) 6070% (d) 8090% 第 29 頁(yè) 共 64 頁(yè) Country: Language: Problem 5: Lewis Structure Total Score: 21 points 51 52 53 54 55 Points 2 4 4 6 5 51 Draw one Lewis structure for each of the following molecules. (a) N2 (b) NH3 (c) O3 (d) SO3 52 Draw the Lewis structure of carbon monoxide and assign formal charges and oxidation states to both the carbon and oxygen atoms in carbon monoxide. T