CH301 Worksheet 1 Answer Key: High School Chemistry Questions. For each problem, identify the kind of question BEFORE answering it. 1. A 25 kg ball has a kinetic energy of 225 J. What is the speed of the ball? What kind of question is this? energy 3 m/s 2. How many molecules of water are there in 100 mL of water? (The density of water = 1.000 g/ml.) What kind of question is this? stoichiometry 3.34 x 1024 molecules 3. Given that the atomic mass of carbon is given as 12.0107 g/mol, what are the approximate relative abundances of the two isotopes 12C and 13C? What kind of question is this? isotopes 98.93% 12C, 1.07% 13C 4. In the electrolysis of 2H2O Æ 2H2 + O2, how many atom of O in O2 are made from 4 g of H2O? What kind of question is this? stoichiometry 1.34 x 1023 molecules 5. What are the most likely ionic forms of (a) sodium and (b) calcium? What kind of question is this? periodic trends (a) Na+; (b) Ca2+ 6. What is the product of a reaction between metallic lithium and oxygen, O2? What kind of question is this? oxidation numbers Li2O 7. Name the following species: (a) Cl-, (b) NO3-, (c) C3H8. What kind of question is this? naming (a) chloride; (b) nitrate; (c) propane 8. The combustion of ethanol has the following equation: C2H5OH + 3 O2 → 2 CO2 + 2 H2O What mass of CO2 is formed from 1 kg of ethanol? What kind of question is this? stoichiometry 1.913 kg 9. Vitamin K contains 78.95% C, 3.95% H, and 21.05% O by mass. What is its empirical formula? What kind of question is this? empirical formula calculation C5H3O 10. Given that vitamin K (see question 9) has molecular weight of 158.15 g/mol, what is its molecular formula? What kind of question is this? molecular formula calculation C10H6O211. When sand is stirred up in a glass of water a (homogeneous of heterogeneous?) mixture is formed. What kind of question is this? Types of mixtures heterogeneous 12. If 10.0 g of hydrochloric acid is dissolved in enough water to make 1.00 liter of solution, what is the molarity of the solution? What kind of question is this? concentration 0.274M 13. Balance the following chemical equation: ____ BCl3 + ____H2O → ____ B(OH)3 + ____HCl What kind of question is this? equation-balancing BCl3 + 3 H2O → B(OH)3 + 3 HCl 14. A microwave oven used radiation at a frequency of 2450 MHz to vibrationally excite water molecules in food. What is the wavelength of this radiation? What kind of question is this? electromagnetic radiation 12.24 cm 15. How may protons, neutrons, and electrons are in the most common atomic form of chlorine? What kind of question is this? subatomic particles 17 protons, 18 neutrons, 17 electrons 16. If 75 mL of water is added to 25 mL of 1 M H2SO4 in water, what is the new concentration of H2SO4? What kind of question is this? dilution 0.25 M 17. Classify the following properties of matter as physical of chemical: (a) color, (b) flammability, (c) density. What kind of question is this? properties of matter (a) physical; (b) chemical; (c) physical 18. Rank the following four forms of electromagnetic radiation in terms of decreasing energy: Microwave, X-ray, radiofrequency, yellow light. What kind of question is this? electromagnetic radiation X-ray > yellow light > microwave > radiofrequency 19. Which of the following is not a strong acid: HI, H2SO4, HCl, or HNO2? What kind of question is this? strong acids HNO2, nitrous acid 20. What is the oxidation number of nitrogen in nitrate? What kind of question is this? oxidation numbers
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