CHEM 103 Exam 1-6 Final - Complete Solutions, Graded A Exam 1-6

CHEM 103 Exam 1-6 Final - Complete Solutions, Graded A Exam 1-6   CHEM 103 Exam 1-6 Final - Complete Solutions, Graded A Exam 1-6 Question 1 1. Convert 1005.3 to exponential form and explain your answer. 2. Convert 4.87 x 10-6 to ordinary form and explain your answer. Answer: 1. Convert 1005.3 = larger than 1 = positive exponent, move decimal 3 places = 1.0053 x 103 2. Convert 4.87 x 10-6 =negative exponent =smaller than 1, move decimal 6 places = 0. Question 2 Using the following information, do the conversions shown below, showing all work: 1 ft = 12 inches 1 pound = 16 oz 1 gallon = 4 quarts 1 mile = 5280 feet 1 ton = 2000 pounds 1 quart = 2 pints kilo (= 1000) milli (= 1/1000) centi (= 1/100) deci (= 1/10) 1. 2.73 liters = ? ml 2. 8.6 pts = ? qts Answer: 1. 2.73 liters x 1000 ml / 1 liter = 2730 ml 2. 8.6 pts x 1 qt / 2 pts = 4.3 qts Question 3 Do the conversions shown below, showing all work: 1. 248oC = ? oK 2. 25oF = ? oC 3. 175oK = ? oF Answer: 1. 248oC + 273 = 521 oK oC → oK (make larger) +273 2. 25oF - 32 ÷ 1.8 = -3.88 oC oF → oC (make smaller) -32 ÷1.8 3. 175oK - 273 = -98 oC x 1.8 + 32 = -144.4 oF oK → oC → oF Question 4 Be sure to show the correct number of significant figures in each calculation. 1. Show the calculation of the mass of a 17.9 ml sample of chloroform with density of 1.49 g/ml 2. Show the calculation of the volume of 19.4 grams of cresol with density of 1.02 g/ml Answer: 1. M = D x V = 1.49 x 17.9 = 26.7 g 2. V = M / D = 19.4 / 1.02 = 19.0 ml Question 5 1. 1.35601 contains ? significant figures. 2. 0.151 contains ? significant figures. 3. 1.35601 + 0.151 = ? (give answer to correct number of significant figures) Answer: 1. 1.35601 contains 6 significant figures. 2. 0.151 contains 3 significant figures. 3. 1.35601 + 0.151 = 1.50701 = 1.507 (to the thousands place for 0.151) Question 6 Classify each of the following as an element, compound, solution or heterogeneous mixture and explain your answer. 1. Honey 2. Hydrogen iodide 3. Tea Answer: 1. Honey - is not on periodic table (not element) - no element names (not compound) appears to be one substance = Solution 2. Hydrogen iodide - is not on periodic table (not element) - has two element names = Compound 3. Tea - is not on periodic table (not element) - no element names (not compound) appears to be one substance = Solution Question 7 Classify each of the following as a chemical change or a physical change 1. A silver spoon forms a black tarnish coating 2. Food is digested 3. Rain freezes on a road on a very cold day Answer: 1. Silver spoon forms black coating - this is Ag → Ag2S (color change) = chemical change 2. Food is digested - breakdown of carbs, proteins, fats to new materials = chemical change 3. Rain freezes on a road on a very cold day - freezing = physical change Question 8 Show the full Nuclear symbol including any + or - charge (n), the atomic number (y), the mass number (x) and the correct element symbol (Z) for each element for which the protons, neutrons and electrons are shown - symbol should appear as follows: xZy+/- n 53 protons, 74 neutrons, 54 electrons Answer:53 protons = I53, 74 neutrons = 127I53, 54 electrons = (+53 - 54 = -1) = 127I53- 1 Question 9 Name each of the following chemical compounds. Be sure to name all acids as acids (NOT for instance as binary compounds) 1. SF6 2. (NH4)3PO4 3. H2S Answer: 1. SF6 - binary molecular = sulfur hexafluoride 2. (NH4)3PO4 - nonbinary ionic = ammonium phosphate 3. H2S - binary acid = hydrosulfuric acid Question 10 Write the formula for each of the following chemical compounds explaining the answer with appropriate charges and/or prefixes and/or suffixes. 1. Iron (III) cyanide 2. Diiodine pentoxide 3. Potassium phosphide 1. Iron (III) cyanide - Fe+3, CN-1 = Fe(CN)3 2. Diiodine pentoxide - ide = binary, two I, 5 O = I2O5 3. Potassium phosphide - ide = binary K+1, P-3 = K3P Question 1 Show the calculation of the molecular weight for the following compounds, reporting your answer to 2 places after the decimal. 1. (NH4)2CrO4 2. C8H8NOI Answer: 1. 2N + 8H + Cr + 4O = 152.08 2. 8C + 8H + N + O + I = 261.05 Question 2 Show the calculation of the number of moles in the given amount of the following substances. Report your answerto 3 significant figures. 1. 12.0 grams of (NH4)2CrO4 2. 15.0 grams of C8H8NOI Answer: 1. Moles = grams / molecular weight = 12.0 / 152.08 = 0.0789 mole 2. Moles = grams / molecular weight = 15.0 / 261.05 = 0.0575 mole Question 3 Show the calculation of the number of grams in the given amount of the following substances. Report your answer to 1 place after the decimal. 1. 1.05 moles of (NH4)2CrO4 2. 1.18 moles of C8H8NOI Answer: 1. Grams = Moles x molecular weight = 1.05 x 152.08 = 159.7 grams 2. Grams = Moles x molecular weight = 1.18 x 261.05 = 308.0 grams Question 4 Show the calculation of the percent of each element present in the following compounds. Report your answer to 2 places after the decimal. 1. (NH4)2SO4 2. C9H9NO3 Answer: 1. %N = 2 x 14.01/132.15 x 100 = 21.20% %H = 8 x 1.008/132.15 x 100 = 6.10% %S = 1 x 32.07/132.15 x 100 = 24.27% %O = 4 x 16/132.15 x 100 = 48.43% 2. %C = 9 x 12.01/179.17 x 100 = 60.33% %H = 9 x 1.008/179.17 x 100 = 5.06% %N = 1 x 14.01/179.17 x 100 = 7.82% %O = 3 x 16/179.17 x 100 = 26.79% Question 5 Show the calculation of the empirical formula for each compound whose elemental composition is shown below. 38.76% Ca, 19.87% P, 41.27% O Answer: 38.76% Ca / 40.08 = 0.9671 / 0.6416 = 1.5 x 2 = 3 19.87% P / 30.97 = 0.6416 / 0.6416 = 1 x 2 = 2 41.27% O / 16.00 = 2.579 / 0.6416 = 4 x 2 = 8 → Ca3P2O8 Question 6 Balance each of the following equations by placing coefficients in front of each substance. 1. C4H10 + O2 → CO2 + H2O 2. P + O2 → P2O5 3. Al + H2SO4 → Al2(SO4)3 + H2 Answer: 1. 2 C4H10 + 13 O2 → 8 CO2 + 10 H2O 2. 4 P + 5 O2 → 2 P2O5 3. 2 Al + 3 H2SO4 → Al2(SO4)3 + 3 H2 Question 7 Classify each of the following reactions as either: Combination Decomposition Combustion Double Replacement Single Replacement