Chem. 1A Midterm 1 Version A Practice Test 2

Transcription

1 Chem. 1A Midterm 1 Version A Practice Test 2 Name Student Number All work must be shown on the exam for partial credit. Points will be taken off for incorrect or no units. Calculators are allowed. Cell phones may not be used for calculators. On short answer problems you must show your work in order to receive credit for the problem. If your cell phone goes off during the exam you will have your exam removed from you. Fundamentals (of 24 possible) Problem 1 (of 8 possible) Problem 2 (of 16 possible) Problem 3 (of 16 possible) Problem 4 (of 12 possible) Multiple Choice (of 24 possible) Midterm Total (of 100 possible) 1

2 Fundamental Questions Each of these fundamental chemistry questions is worth 3 points. You must show work to get credit, if applicable. Little to no partial credit will be rewarded. Make sure to report answers in the correct number of significant figures and indicate the proper units. 1) 3 pts How many kilograms are in 3251 mg? 2) 3 pts What ionic compound is formed between a) calcium and bromine and b) potassium and oxygen? 3) 3 pts Balance the following equations? a) MnO 2 (s)+ HCl(aq) Cl 2 (aq)+ MnCl 2 (aq)+ H 2 O(l) b) BCl 3 (g)+ H 2 O(l) B(OH) 3 (aq)+ HCl(aq) 4) 3 pts What are the names of the following elements: Mo, Mg, and Sn? 5) 3 pts What are the names of the following compounds: a) SF 6 and b) AlF 3? 6) 3 pts How many moles of Cu are in 3.20 g? 7) 3 pts How many protons, neutrons, and electrons does a) neon-22 and 3 b) Bi have? 8) 3 pts How many widgets are in moles? 2

3 Short Answer Questions Each of the following short answer questions are worth the noted points. Partial credit will be give. You must show your work to get credit. Make sure to report answers in the correct number of significant figures and indicate the proper units. 1) 8 pts An iron bar weighed 664 g. After the bar had been standing in moist air for a month, exactly one-eighth of the iron turned to rust (Fe 2 O 3 ). Calculate the final mass of the iron bar and rust. 2) A solid compound x contains 63.3% Mn and 36.7% O by mass. When X is heated, oxygen gas is evolved and a new solid compound Y containing 72.0% Mn and and 28.0% O is formed 2a) 6 pts Determine the empirical formula of X. Question 2 Continues on Page 4 3

4 2b) 6 pts Determine the empirical formula of Y. 2c) 4 pts Write a balanced equation for the conversion of X to Y. 3) DDT, an insecticide harmful to fish, birds, and humans, is produced by the following reaction: 2C 6 H 5 Cl(l) + C 2 HOCl 3 (l) C 14 H 9 Cl 5 (l) + H 2 O(l) C 6 H 5 Cl chlorobenzene, C 2 HOCl 3 chloral, and C 14 H 9 Cl 5 DDT In a government lab, 1142 g of chlorobenzene is reacted with 485 g of chloral. 3a) 7 pts What is the mass of DDT formed? Question 3 Continues on Page 5 4

5 3b) 1 pts Which reactant is limiting? Which is in excess? 3c) 4 pts What mass of the excess reactant is left over? 3d) 4 pts If the actual yield of DDT is g, what is the percent yield? 4) Convert the following into balanced equations 4a) 4 pts When gallium metal is heated in oxygen gas, it melts and forms solid gallium(iii) oxide. 4b) 4 pts When solutions of calcium chloride and sodium phosphate are mixed, solid calcium phosphate forms and sodium chloride remains in solution. 4c) 4 pts When crystalline potassium chlorate is heated to just above its melting point, it reacts to form two different crystalline compounds, potassium chloride and potassium perchlorate. 5

6 Multiple Choice Questions Each of the following multiple choicee questions are worth 4 points. Your answers need to be filled in on the Scantron provided. Note: Your Scantrons will not be returned to you,, therefore, for your records, you may want to mark your answers on this sheet. On the Scantron you need to filll in your perm number, testt version, and name. Failure to do any of these things will result in the loss of 1 point. Your perm number is placed and bubbled in under the ID number. Do not skip boxes or put in a hyphen. In addition, leave bubbles blank under any unused boxes. The version number (A) is bubbled in under the test form. 1. Compound X 2 Y is 60% X by mass. Calculate the percent Y by masss of the compound X 2 Y 2. A) 50% B) 20% C) 30% D) 40% E) None of the above. 2. Which of the following is not the correct chemical formula for the compound named? A) All of the formulas are correct. B) Fe 2 O 3 iron(iii) oxide C) PBr5 phosphorus pentabromidee D) CoO cobalt(ii) oxide E) CaSO calcium sulfite O 4 3. For a new element, 67.16% is an isotope with mass amu, 2.76% is an isotope with mass amu, and 30.08% is an isotope with mass amu. Calculate the average atomic masss of this new element. A) amu B) amu C) amu D) amu E) None of the above. 4. What is the correct formula for chromium(vi) oxide? A) CrO3 B) Cr 2 O 3 C) Cr 6 O D) CrO6 E) None of the above. 6

7 5. Consider the following balanced equation: A(g) + 5B(g) 3C(g) + 4D(s) When equal masses of A and B are reacted, which is limiting? A) If the molar mass of A is less than the molar mass of B, then B must be limiting. B) More information is needed. C) If the molar mass of A is greater than the molar mass of B, then A must be limiting. D) If the molar mass of A is less than the molar mass of B, then A must be limiting. E) If the molar mass of A is greater than the molar mass of B, then B must be limiting. 6. How many of the following chemical formulas are written incorrectly? ClNa BaBr 2 LaF 2 ClRb A) All are written incorrectly. B) One is written incorrectly. C) Two are written incorrectly. D) All are written correctly. E) Three are written incorrectly. 7