HighFour Chemistry Category C: Grades 9 – 10 Round 6 Monday, February 13, 2017 The use of calculator is required. Question #1 Question #2 Question #3 An excerpt from the periodic table of elements is shown. Which element has the greatest electron affinity? Write the chemical name of your answer. A steel tank contains an unknown gas at 25°C and is at a pressure of 10.0 atm. What is the internal gas pressure when the tank and its contents are heated to 120°C? During an experiment, ammonia gas reacts with oxygen gas to form nitrogen dioxide and water. The reaction can be written as: NH3 + O2 ⟶ NO2 + H2O Balance the above reaction and determine the stoichiometric coefficient for oxygen gas. Question #4 Question #5 What is the chemical name of the halogen that can be found in period 4? Glycerol is a colorless, viscous liquid that is usually being used as a sweetener in the food industry and as a humectant in pharmaceutical industries. Its chemical formula is C3H8O3. What is the weight of 1 mole of glycerol? Express your answer in terms of grams. HighFour Chemistry Category C: Grades 9 – 10 Round 6 Monday, February 13, 2017 The use of calculator is required. Question #6 Question #7 Question #8 Question #9 Question #10 How much volume of a 19.5 M NH3 (in mL) is needed to make a 500.0 mL of a 0.75 M solution? The following configuration 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p3 is the ground state electron configuration for the element __________. Identify the name of the element. Cerussite is a mineral ore of lead, and it consists of lead carbonate (PbCO3). It was an important component in the production of lead paints, which is now discontinued due to its hazardousness. Calculate the mass of PbCO3 if it contains 50.0 grams of Pb. Half-­‐life refers to the nuclide's decay rate. It describes the time it takes for one-­‐half of a sample to disappear. If the half-­‐life of plutonium-­‐239 is 2.44 x 104 years, what fraction of plutonium-­‐239 is left after 7.32 x 104 years? Assume that the original amount of Plutonium-­‐239 is 1 unit. What is the name of NaC2H3O2? HighFour Chemistry Category C: Grades 9 – 10 Round 6 Monday, February 13, 2017 The use of calculator is required. Question #11 Question #12 Question #13 Question #14 Question #15 Urea is the organic compound which was used to disprove the theory that organic chemistry is the chemistry of compounds derived from living things. It was synthesized from ammonium cyanate, an inorganic compound. Urea has the chemical formula NH2CONH2. How many elements are there in the chemical formula of urea? What is the concentration, in mol/L, where 100 g of NaCl has been dissolved in enough water to make 500 mL of solution? During the formation of ionic compounds, the ions are attracted to several of the oppositely-­‐charged ions. The ions organize themselves into patterns. What do we call these organized patterns of positive and negative ions? A nuclide is a particular type of nucleus characterized by a specific atomic number and nucleon number. If the most abundant nuclide of uranium has 146 neutrons and 92 protons, what is the nucleon number of this particular nuclide? What is the charge of the cation in Cu2O? HighFour Chemistry Category C: Grades 9 – 10 Round 6 Monday, February 13, 2017 The use of calculator is required. Question #16 Question #17 Question #18 Question #19 Question #20 What do we call the substance that speeds up the rate of the reaction without being consumed by the reaction? A group of friends buys beverages for a party they're hosting. They buy an equal number of bottles of two sizes. The total volume of all the bottles of the first size is 42.5 L and the total volume of the second size is 20.5 L. What is the ratio of volumes of the first size of beverage to the second? A sample of gas initially occupies 430.0 mL at 1.50 atm. What is the pressure required (in atm) to reduce its volume to 295.5 mL at constant temperature? The table below shows the number of neutrons and protons for the most abundant isotopes of the following elements. Based on these data, calculate the neutron-­‐to-­‐proton (no. of neutron per 1 proton) ratio of the element with a chemical symbol of Sb. Element No. of Protons No. of Neutrons Bismuth 83 126 Phosphorus 15 16 Antimony 51 70 Arsenic 33 42 What do we call the phase change where gas changes to liquid?