Chemistry 11 practice test with answers

Unit 3 Toombs CHEMISTRY  11 STOICHIOMETRY PRACTICE TEST Use these questions as a guide as a START to your studying. Each question below represents a concept and type of question that you should feel confident completing. If you have difficult with one of the questions below, then you should go back to your notes and worksheets to more fully review and practice this concept. Be sure to use the resources (TUTORIAL VIDEOS!) on the website to help you fully understand these concepts. Just completing these 10 questions IS NOT ENOUGH to adequately prepare you for the test. REDOX EQUATIONS Balance the following REDOX equations: 1. a) b) Fe Al + Ag+ à Ag + Pb+2 à Pb + Fe+2 + Al+3 ACTIVITY SERIES Complete the following single replacement reactions: 2. a) Cu + H2O à b) Cl2 + NaIà ENERGY in CHEMICAL REACTIONS 3. Define and draw a diagram for an exothermic reaction and an endothermic reaction. In your answer, explain how stoichiometry affects the kJ of energy involved in a reaction. PERCENT COMPOSITION, EMPIRICAL FORMULA 4. Find the percent composition of Rhodium (IV) cyanide. Report your percentages to 3 significant figures. 5. Calculate the empirical formula for each compound: a) 7.20% P, 92.8% Br b) 43.7% Zr, 10.3% B, 46.0% O Name this compound YOU MUST SHOW YOUR PROCESS VERY CLEARLY IN ORDER TO OBTAIN FULL MARKS FOR THESE CALCULATION QUESTIONS. PERCENT COMPOSITION, EMPIRICAL FORMULA, MOLECULAR FORMULA 6. a) An unknown sample has 47.08 % C, 6.59 % H, and 46.33 % Cl. What is its empirical formula? b) For the example above, if the molar mass of the actual compound is 153 g/mol, what is its molecular formula? 7. An unknown compound was found to have a percent composition as follows: 47.0 % potassium, 14.5 % carbon, and 38.5 % oxygen. What is its empirical formula? If the true molar mass of the compound is 166.22 g/mol, what is its molecular formula? What is the name of this compound? MOLECULAR FORMULA…and STOICHIOMETRY 8. 27.0 g of Aluminum reacts with 201.25 g of copper chloride in a single replacement reaction to produce Copper metal and 133 g of aluminum chloride. What is the formula of the copper chloride? Are you determining an empirical or molecular formula in this case? (Since Copper is a transition metal, we don’t know if it’s charge in the copper chloride is +1 or +2, so we don’t know what this reactant originally looked like). STOICHIOMETRY 9. If 4.11 g of Iron are added to 317 mL of Hydrogen Sulphide gas at STP, will both reactants be totally consumed? What mass of products will we obtain? 10. 35.0 a) b) c) d) g of copper (II) iodide reacts with 39.0 g of silver nitrate. calculate the grams of each product formed state the limiting reagent determine the amount, in grams, of the excess reagent show your check of the law of conservation of mass YOU MUST SHOW YOUR PROCESS VERY CLEARLY IN ORDER TO OBTAIN FULL MARKS FOR THESE CALCULATION QUESTIONS. 11. a) Calculate the theoretical yield of C2H5Cl if 112 g of C2H5OH is reacted with 34.7 g of PCl3, forming C2H5Cl and H3PO3. b) If 23.7 g of C2H5Cl is produced, what is the percent yield? 12. Uranium reacts with Bromine to form Uranium (VI) bromide in a synthesis reaction. If the reaction starts with 100. g of Uranium and the percent yield of this reaction is 83%, what is the actual yield of Uranium (VI) bromide? ANSWER KEY 1 a) Fe + 2Ag+ à 2Ag + Fe+2 b) 2Al + 3Pb+2 à 3Pb + 2Al+3 2 a) Cu + H2O à no reaction !!! + Copper is below H on the activity series chart and therefore will not replace the H+ in water (or in an acid!) b) Cl2 + 2NaI à I2 + 2NaCl Chlorine is above Iodine on the Activity series chart so a single replacement DOES occur. 3. See your own notes and the detailed notes posted on the website! The amount of energy produced or absorbed in a chemical reaction is directly proportional to the moles of product produced. Stoichiometry (mole ratios) affect the energy of a reaction. ANSWER KEY 4 49.3% Rh 23.4 % C 27.3 % N 5. a) PBr5 b) Zr(BO3)2 Zirconium (VI) borate 6. 7. a) C3H5Cl b) C6H10Cl2 empirical: KCO2 molecular: K2C2O4 name: Potassium oxalate 8. You will be setting up a balanced equation. Using the Law of Conservation of mass (FIRST!) you will be using Mole stoichiometry to determine the balanced equation. THEN you will be able to determine the formula: CuCl2 This is a molecular formula (because the copper (II) chloride actually looks like this) BUT this is also the empirical formula, because ionic compounds are ALWAYS expressed in lowest terms. 9. No, both reactants will NOT be totally consumed. (In other words, this is a limiting and excess reagents problem) Products formed: 1.25 g FeS and 0.0286 g H2 10. a) 20.6 g Cu(NO3)2 and 51.6 g AgI b) CuI2 is the limiting reagent c) 1.7 g AgNO3 excess (note: depending on SF, you may have 1.6 g as an answer) d) 35.0 g + 39.0 g = 51.7 g + 20.6 g + 1.7 g Another way to show the check: 35.0 + (39.9 – 1.7) = 51.7 + 20.6 35.0 + 37.4 = 51.7 + 20.6 11. a) 49.0 g C2H5Cl b) 48.4 % 12. 250 g of UBr6 2 SF You should be able to complete a test on this material in 70 minutes. (Note that there are 9 different types of questions)