Title DCC Part I - Final.pdf ✅

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
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 Cu 2+ . The relationship between the fluorescence intensity of ZnO@MOF and the concentration of Cu 2+ in a certain range is shown below. 7.5×10 -3 g of copper-containing ceruloplasmin (M = 1.5×10 5 ) was under pre-treatment, and all Cu in the protein was converted to Cu 2+ 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) Ba 2+ DChO Chemistry Competition 2024 - Part I Written by Dr. Chen and his team National Mock
3/25 T1 1 pt T2 1 pt T2 1 pt T2 1 pt Question 6 of 60 An octahedral chromium complex has the empirical formula of CrH12O6Cl3 (M = 266 g/mol). When the complex is gently heated, there is a 6.76% loss in mass. If 1.00 g of this complex is dissolved in water and with excessive AgNO3 solution added, what is the mass of precipitate produced? A) 0 g B) 0.54 g C) 1.08 g D) 1.62 g Question 7 of 60 Peter wants to measure 10 mL of water to dissolve a certain amount of potassium hydrogen phthalate in a flask, which is later used for the standardization of a sodium hydroxide solution, which of the following apparatus is most suitable? A) 10 mL volumetric flask B) 10 mL volumetric pipette C) 10 mL graduated cylinder D) Buret Question 8 of 60 Which of the following solutions has the longest shelf life? A) KI(aq) B) FeCl3 (aq) C) FeSO4 (aq) D) Na2C2O4 (aq) Question 9 of 60 When a 0.1 M sodium thiosulfate is acidified by sulfuric acid, what is observed? I. A precipitate forms. II. Gas is evolved. A) I only B) II only C) Both I and II D) Neither I nor II DChO Chemistry Competition 2024 - Part I Written by Dr. Chen and his team National Mock
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