1/25 Name: ____________________________ Date: ____________________________ Signature: ____________________________ T1 1 pt T1 1 pt Test: DCC 2024 Part I (Available on Mar 25-31) Points: 60 points Score: ____________ Question 1 of 60 When 3.0 moles of N2 react with 2.0 moles of H2, what is the maximum volume of NH3 at STP? A) 7.5 L B) 15 L C) 23 L D) 30. L Question 2 of 60 1.12 g amino acid with a molecular formula of CaHbNxO2 is completely combusted to produce 1.70 g CO2, 0.811 g H2O, and 0.360 g of N2. What is the value of x in its formula? A) 1 B) 2 C) 4 D) 8 DChO Chemistry Competition 2024 - Part I Written by Dr. Chen and his team National Mock ߝ ⋎ sǎii Tip V n 13310.08206273.2 29.8L D or V 1.33 22.4 29.8L n c 447 0.0386mi n H 2x 98 0.0901molly n N 2 038 0.0257m1 n 0 1 12 0.0386x12i 0.0901 0.0257x14.0 o0129mol ኞԫ 0 ߝ2셈 57g x 4 C The annotations for Q1-Q30 were written by Yiwei Liang, and for Q31-60 60 by Dr. Chen. If you see any “bugs”, please reach out to Dr. Chen at
[email protected].
2/25 T1 1 pt T1 1 pt T1 1 pt Question 3 of 60 A ZnO@MOF fluorescent material was synthesized for the detection of Cu2+. The relationship between the fluorescence intensity of ZnO@MOF and the concentration of Cu2+ in a certain range is shown below. 7.5×10-3 g of copper-containing ceruloplasmin (M = 1.5×105) was under pre-treatment, and all Cu in the protein was converted to Cu2+ and diluted to a volume of 1.0 L. The measured fluorescence intensity was 10.2. What is the number of copper atoms contained in one molecule of ceruloplasmin? A) 1 B) 2 C) 4 D) 8 Question 4 of 60 A solution is made of 3.00 g metal sulfate, 9.00 sucrose (M = 342 g/mol), and 180 g H2O (M = 18.0 g/mol). If the solution has an osmotic pressure of 11.6 bar at 298 K. What is the identity of the metal? Assuming the density of the solution obtained is 1.00 g/mL. A) Li B) Na C) Mg D) Al Question 5 of 60 20.0 mL of 0.15 M aqueous KAl(SO4)2 and 10.0 mL of 0.35 M Ba(OH)2 are mixed, giving a white precipitate. Which ion is MOST abundant in the supernatant? A) OH− B) SO4 2− C) Al 3+ D) Ba2+ DChO Chemistry Competition 2024 - Part I Written by Dr. Chen and his team National Mock T According to the graph 4 òԫ 8.0 Intensity10.2 v 4 106M Cn i n Cu J CV 1.0 0.4x106 D 4.0x10ጱ1 D nccerul.plasmin i5 5.0 108mol T iCRT fiݣ 2 604i93220100 0.427 B ic 298f 08314 0.468M t'i 43 230320io0 4 0.330 i Csufeel 0.468 Csucroseԫ0Ӟ468Ӟ ࿈ e similarly bothߝitsforMgand 0.468 13.0g 1807x103 ԫ0.331M Al doesn'tmatch0.331 asNa sothe9 Molesofeach ion beforemixing on 7103m1 504ԧ6103 A13 3x103m1 Batty 3.5x103mn1 B Precipitate formed AllOH3 Bas04 i molesofeachdon aftermixing most ๕ߝabnndgzj ߝ 0i Bior.no iߝi ݣߝ25
4/25 T2 1 pt T2 1 pt T2 1 pt Question 10 of 60 AgI is a pale yellow precipitate, which of the following reagents dissolve it the best? A) Concentrated NH3(aq) B) Na2S2O3(aq) C) NaCN(aq) D) Na2S(aq) Question 11 of 60 A student is given the task of determining the iodine content of tablets that contain KI and an inert, water- soluble sugar as a filler. A tablet is dissolved in 50.0 mL of distilled water, and an excess of 0.20 M Pb(NO3)2(aq) is added to the solution. A yellow precipitate forms, which is then filtered, rinsed, and dried. Which of the following causes a higher iodine percentage than the actual value? A) A vacuum filtration is used instead of a gravity filtration to get the precipitate. B) A larger amount of water is used to rinse the precipitate. C) A wrong formula of PbI is used to calculate the iodine content. D) The precipitate is not rinsed. Question 12 of 60 An artificial crude benzoic acid sample contains a small amount of NaCl, what is the best method to purify the sample? A) Filtration B) Recrystallization C) Neutralization D) Distillation DChO Chemistry Competition 2024 - Part I Written by Dr. Chen and his team National Mock ԫ use todissoleAgaformAgNH Ii CantdissoleAg Ifl use to dissole AgBr formAg52037 i cant dissolveAgI usedto dissolveAgt formAgCarli willform new precipitateAgzs Nodiference i ExcesswaterwilldissolvesomePbIz leadingto Somesolublecontentremains in üinǎiǒiii㥼 㥼iii leading to ahigheriodinecontent pg Both benzoic acid BA and Nad are solublein waterthough BAis muchlesssoluble therefore by recrystallization the BA will recrystallize While Nacl remain soluble in water In sucha way the sample will be purifiedas Nacl isremoved Full procedure Dissolvethecrudesamplein asmall amountofwaterunderheatto prepare a hot saturated solutionof benzoic acid Cool down to room temperature leading to recrystallization ofbenzoicacidsince its solubility decreases with temperature significantyl TheNalldissolves well in waterandwillnot crystallize
English