Name Veritas Class Period Chemistry: Final Exam Practice Problems The final exam will focus on material covered in the spring semester. However, note that much of the material learned early in the year has carried over into these units. This review guide is the minimum of what should be completed in preparation for the final. Review old quizzes, tests, review guides, and worksheets. What are the seven diatomic elements? Find the molar mass of the following: a. KNO 3 d. oxygen gas b. (NH 4 ) 2 CO 3 e. Ca(NO 3 ) 2 Convert from g à moles or from moles à g. Show units and correct SFs. a. 0.476 g of (NH 4 ) 2 SO 4 x = moles b. 0.15 moles NaNO 3 x = g How did JJ Thomson conclude that the mobile charged particle in the atom had a ( ) charge. Below left is a 2-D array that represents an ionic solid. At right is a 2-D array that represents a molecular solid. Discuss at least four differences between ionic and molecular substances. 359
Which combinations of elements give rise to ionic compounds and which form molecular compounds? (In other words, how do you recognize, based on a formula alone, whether a compound is ionic or molecular?) Write M for molecular compounds and I for ionic compounds. Then, write the correct name for the compound. PBr3 CO2 KOH FeCl3 Hg(OH)2 Cu2O Identify the following compounds as ionic or molecular. Provide the correct formula for each compound. Ionic or Molecular Name A. diphosphorous pentoxide_ B. ammonium nitride C. calcium oxalate D. potassium oxide E. tin (IV) bromide F. mercury (I) bromide Define/Discuss the following terms: Coefficients Subscripts Endothermic Exothermic Conservation of Mass Aqueous solution 360
Directions: Balance the following chemical reactions (including state subscripts) and then provide the type of chemical reaction. Oxygen gas plus nitrogen gas reacts to form nitrogen dioxide gas Aqueous beryllium iodide reacts with aqueous tin (II) nitrate to form aqueous beryllium nitrate and solid tin (II) iodide. Aqueous ammonium sulfate reacts with aqueous lead (II) chlorate to form aqueous ammonium chlorate and solid lead (II) sulfate. Aqueous hydrogen carbonate decomposes to give liquid water and carbon dioxide gas. Liquid water reacts with carbon monoxide gas to produce hydrogen gas and carbon dioxide gas. Directions: Determine for each of the following reactions if the reaction is endothermic or exothermic. Balance the equations. C + O2 CO + energy Type N2O4 + energy N2 + O2 Type CaCl2 + O2 CaO + Cl2 + energy Type SO2 + CO2 + energy SO3 + CO Type 361
Directions: Balance the following chemical reactions. If no reaction occurs, write no reaction. Solid zinc metal is placed into an aqueous solution of silver nitrate. Heptane (C7H16) burns readily in the presence of air. Aqueous calcium chloride is mixed with sulfuric acid. Phosphorus trichloride decomposes when heated strongly in a test tube. Directions: For each of the reactions below, write the balanced chemical equation, including the energy term on the correct side of the equation. Then represent the energy storage and transfer using the bar graphs. When you heated sodium hydrogen carbonate, you decomposed it into sodium oxide, water vapor, and gaseous carbon dioxide. 362
When solid zinc was added to hydrochloric acid, the products were hydrogen gas and an aqueous solution of zinc chloride. You could feel the test tube get hotter. What observations did you note from the chemical reactions lab to identify if a reaction occurred? Draw a chemical potential energy curve for an exothermic reaction and for an endothermic reaction. Use balanced equation and the BCA table to predict the quantity of reactant or product involved in a chemical reaction. Calculate the number of grams of potassium chloride, KCl, that will be formed by the decomposition of 6.45 g of potassium chlorate, KClO 3. 363
Determine percent yield when actual yield is known. A chemist burns 160 g of Al in air to produce 260 g of solid aluminum oxide. Determine the theoretical yield. Determine the percent yield. Determine the limiting reactant and stoichiometry Phosphorus and bromine react vigorously together to form phosphorus tribromide. If 5.0 g of phosphorus and 35 g of bromine react, how many grams of PBr3 could be produced? Stoichiometry involving gases Nitrogen gas and hydrogen gas combine to produce ammonia gas. What volume of hydrogen gas at STP is required to react completely with 1.50 moles of nitrogen gas? Consider the following reaction: P 4 (s) + 6 H 2 (g) 4 PH 3 (g) What volume of hydrogen gas at laboratory conditions of 25.0 C and 0.981 atm is required to react completely with 42.85 grams of P 4? 364
Stoichiometry involving solutions What is the molarity of a solution that contains 125 grams of NaCl in 4.00 L of solution? Solid iron (III) chloride can be produced by reacting aqueous iron (III) oxide with a hydrochloric acid solution. How many milliliters of a 6.00M HCl solution are needed to react with excess Fe2O3 to produce 16.5 grams of solid FeCl3? (NOTE: The second product is liquid water.) Calculate the ppm for the following problems: a. 2.50 grams of solute dissolves in 3,500,000 grams of water. b. 4.01 x 10-3 grams of salt is in 675,000 grams of water. c. 5.00 mg of lead is in 2.00 kg of water. Solubility Curve Problems: Which is more soluble NaNO3 or KCl? How does the line drawn for a particular substance relate to the saturation of a solution of that substance? How many grams of NH4Cl will dissolve in 100 grams of 90 C water? 365
Stoichiometry Including Energy Changes (ΔH) Solid tin metal reacts with chlorine gas forming liquid tin (IV) chloride according to the reaction shown below: Sn (s) + 2Cl2 (g) à SnCl4 (l) ΔH = -511 kj What volume of chlorine gas (at laboratory conditions of 760.0 mm Hg and 25 o C) is required in order for the reaction to release 328 kj of heat energy? Draw and label Thomson's "Plum-pudding" Model of the atom and Rutherford's Model of the Atom. Compare and contrast the two models. How did Rutherford come to his conclusion? How did Niels Bohr improve Rutherford's model of the atom? Discuss the changes. Draw Bohr's model of the atom. Periodicity: Explain/Discuss the periodic trends in atomic radii and ionization energy. 366
Measurement and Calculations: 1. Demonstrate understanding of the use of measurements in science. -You should be able to apply the rules of significant figures to choose answer with the correct number of significant figures. -Express the answer in the correct number of significant figures. Label with appropriate units. a. 21.3 g = 16.384615 1.3 cm 3 b. 6.34 cm 2 x 1.2 cm = 6.251437 1.217 cm c. 13.21m + 61.5 m = 74.71 You should also be able to measure the length of an object or volume of a liquid to the appropriate number of significant figures based upon the measuring instrument. Which of the following best expresses the width of the business card? a. 5 cm b. 5.0 cm c. 5.05 cm d. 5.50 cm Demonstrate proficiency in the use of scientific notation and use of dimensional analysis in metric conversions. -Know the meaning of the following metric prefixes and be able to make conversions utilizing them: milli-, centi-, kilo- Example: 1m 150mm 1000mm = 0.15m Complete the indicated conversions: a. 37 g x = mg c. 138 m x = km b. 4.7 kg x = g d. 4021 mm x = 367
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