CHEMISTRY 102B Practice Hour Exam I. Dr. D. DeCoste T.A (30 pts.) 16 (15 pts.) 17 (15 pts.) Total (60 pts)

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1 CHEMISTRY 102B Practice Hour Exam I Spring 2016 Dr. D. DeCoste Name Signature T.A. This exam contains 17 questions on 5 numbered pages. Check now to make sure you have a complete exam. You have one hour and thirty minutes to complete the exam. Determine the best answer to the first 15 questions and enter these on the special answer sheet. Also, circle your responses in this exam booklet. Show all of your work and provide complete answers to questions 16 and (30 pts.) 16 (15 pts.) 17 (15 pts.) Total (60 pts) Useful Information: L = ml N A = x Solubility Rules: 1. Most nitrate salts are soluble. 2. Most salts of sodium, potassium, and ammonium cations are soluble. 3. Most chloride salts are soluble. Exceptions: silver, lead(ii), and mercury(i) chloride. 4. Most sulfate salts are soluble. Exceptions: calcium, barium, and lead (II) sulfate. 5. Most hydroxide salts can be considered insoluble. Soluble ones: sodium, potassium, and calcium hydroxide. 6. Consider sulfide, carbonate, and phosphate salts to be insoluble.

2 Practice Hour Exam I Page No Consider the measurements 8.74 m and 1.59 m. If we add these measurements we should record the answer to significant figures, and if we multiply these measurements we should record the answer to significant figures. a) 3, 3 b) 4, 4 c) 3,4 d) 4,3 e) none of these 2. The most stable ion for barium in a compound has protons and electrons. a) 58, 56 b) 54, 56 c) 56, 56 d) 56, 58 e) 56, You purchase a 5.00 lb. bag of sugar (C 12 H 22 O 11 ) at the grocery store. How many grams of sodium chloride must you buy so that you have the same number of sodium ions as sugar molecules? Note: 1 lb. = 1 pound = g a) 154 g b) 387 g c) 892 g d) 2,270 g e) None of these 4. Which of the following compounds has the largest molar mass? a) barium phosphate b) aluminum phosphate c) cesium phosphate d) iron(iii) phosphate e) potassium phosphate 5. You have a sample of zinc (Zn) and a sample of aluminum (Al). You have an equal number of atoms in each sample. Which of the following statements concerning the masses of the samples is true? a) The mass of the Zn sample is more than twice as great as the mass of the Al sample. b) The mass of the Zn sample is more than the mass of the Al sample, but it is not twice as great. c) The mass of the Al sample is more than twice as great as the mass of the Zn sample. d) The mass of the Al sample is more than the mass of the Zn sample, but it is not twice as great. e) The masses of each sample are equal. 6. The percent by mass of carbon is 20.0% for a species containing only carbon and oxygen. Which of the following could be this species? a) Carbon dioxide b) Carbon monoxide c) The carbonate ion. d) The oxalate ion (C 2 O 4 2- ) e) None of these (a-d). 7. Which of the following has the highest percent by mass of sulfur? a) Sodium sulfate b) Sulfur dioxide c) Sulfuric acid (H 2 SO 4 ) d) Cobalt(III) sulfide e) Sulfur tetrafluoride

3 Practice Hour Exam I Page No You find the following chemical equation scratched into the wall of your dorm room: 2A +?B C + 4D You cannot read the coefficient in front of B. However, you know that equal masses of A and B are required so that there are no reactants left over and that the molar mass of A is greater than the molar mass of B. Which of the following is true? a) The coefficient in front of B must be greater than 2. b) The coefficient in front of B must be less than 2. c) The coefficient in front of B must be equal to 2. d) More information is needed to answer this question. e) None of the above choices (a-d) is true. 9. Consider the reaction as represented by the following unbalanced chemical equation H 2 (g) + O 2 (g) H 2 O (g) You react 10.0 g of hydrogen gas with 60.0 g oxygen gas. Determine the amount of reactant in excess after the reaction is complete. a) 20.3 g of oxygen gas remains after the reaction is complete. b) 17.1 g of oxygen gas remains after the reaction is complete. c) 6.22 g of hydrogen gas remains after the reaction is complete. d) 2.44 g of hydrogen gas remains after the reaction is complete. e) Neither reactant is in excess. 10. Which of the following statements is true concerning a reaction represented by the following balanced chemical equation? 2C 2 H 6 (g) + 7O 2 (g) 6H 2 O(l) + 4CO 2 (g) a) If we have equal masses of C 2 H 6 and O 2 there is no limiting reactant. b) If we have an equal number of moles of C 2 H 6 and O 2 there is no limiting reactant. c) If we have more mass of C 2 H 6 than O 2, then O 2 must be limiting. d) If we have more mass of O 2 than C 2 H 6, then C 2 H 6 must be limiting. e) At least two of the above (a-d) are true. 11. Which of the following solutions contains the greatest number of ions? a) ml of 1.00 M sodium chloride b) ml of 1.00 M magnesium chloride c) ml of 1.00 M iron(iii) chloride d) ml of 1.00 M cobalt(ii) chloride e) All of the above solutions (a-d) contain the same number of ions.

4 Practice Hour Exam I Page No You have equal masses of different solutes dissolved in equal volumes of solution. Which of the solutes would make the solution with the highest concentration measured in molarity? a) LiCl b) KCl c) KOH d) NaOH e) All the same 13. You mix ml of M calcium chloride with ml of M silver nitrate. Which ions are in solution when the reaction is complete? a) calcium ion, chloride ion, silver ion, nitrate ion b) chloride ion, silver ion, nitrate ion c) calcium ion, chloride ion, nitrate ion d) calcium ion, nitrate ion e) calcium ion, silver ion, nitrate ion 14. Calculate the concentration of chloride ions when ml of M sodium chloride is mixed with ml of M magnesium chloride. a) M b) M c) M d) M e) none of these 15. You mix ml of M aqueous sodium phosphate with ml of M aqueous calcium nitrate. What mass of solid forms? a) g b) 1.03 g c) 1.35 g d) 1.55 g e) 3.10 g

5 Practice Hour Exam I Page No Copper metal reacts in a solution of silver nitrate according to the following unbalanced equation Cu(s) + AgNO 3 (aq) Ag(s) + Cu(NO 3 ) 2 (aq) You place 5.00 g of copper in a large beaker with 60.0 ml of 3.00 M aqueous silver nitrate solution. Determine what is left in the beaker after the reaction has gone to completion. That is, the mass(es) of any solid(s) and the concentration(s) of any ion(s) present in the water. Show all work.

6 Practice Hour Exam I Page No A g sample consisting of a mixture of sodium chloride and potassium sulfate is dissolved in water. This aqueous mixture then reacts with excess aqueous lead(ii) nitrate to form g of solid. Calculate the percent by mass of sodium chloride in the original mixture. Show all work.