Chem103.M1ProblemSet

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Chemistry

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Feb 20, 2024

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Chemistry Module 1 Review Question 1 Convert the following numbers from one form to another and explain your answer. 1.) 5.38 x 10 -3 = _____________ 2.) 623000000. = _____________ 1) 5.38 x 10 -3 = .00538 Since the exponent is negative, then the ordinary number is going to be <1 • decimal moves 3 spots to the left 2) 623000000 = 6.23 x 10 8 The number is >1, so the exponent will be positive. • decimal moves 8 spots to the left 1.) 5.38 x 10 -3 = negative exponent = smaller than 1, move decimal 3 places = 0.00538 2.) 623000000. = larger than 1 = positive exponent, move decimal 8 places = 6.23 X 10 8 Question 2 Complete the following conversions and show all work. Be sure to write your answer with the correct units. 1.) 25.3 g = __________ decigrams 2.) 56 ft = __________ in 1) 25.3 g = ? decigrams 25.3 x 10 decigrams/1 g = 253 decigrams 2) 56 ft = ? in 56 x 12 in/1 ft = 672 in 1.) 25.3 g x 10 dc / 1 g = 253 dg 2.) 56 ft x 12 in / 1 ft = 672 in Question 3 Complete the following conversions and show all work. Be sure to write your answer with the correct units. 1.) 85 o F = ___ o C 2.) 412 o K = ___ o F

1) (85-32)/1.8 = 29.4 o C 2) 412 - 273 = 139 o C 139 x 1.8 + 32 = 282.2 o F 1.) 85 o F - 32 ÷ 1.8 = 29.4 o C 2.) 412 o K - 273 = 139 o C x 1.8 + 32 = 282.2 o F Question 4 Complete the following problems and show all work. Be sure to show the correct number of significant figures in each calculation and answer with the correct units. 1.) What is the volume of a sample of mercury (d = 13.6 g/ml) which weighs 1000. g? 2.) What is the density of 200. ml of bromine which weighs 620. grams? 1) v = m/d 1000/13.6 = 73.529 v = 73.529mL 2) d = m/v 620/200 = 3.1 d = 3.1 g/mL 1.) 13.6 g/ml = D 1000 g = M find V = M / D = 1000 / 13.6 = 73.5 ml 2.) 200 ml = V 620 g = M find D = M / V = 620 g / 200 ml = 3.10 g/ml Question 5 Complete the following problems and show all work when necessary. Be sure to show the correct number of significant figures in each calculation and answer with the correct units. How many significant figures are there in each of the following numbers? 1.) 306.2 2.) 0.0231 3.) What is the mass of a sample of lead (d = 11.35 g/ml) which has a volume of 85.0 mL? 1) 4 2) 3 3) m = d x v 11.35 x 85.0 = 964.75 m = 965 g 1.) 306.2 contains 4 significant figures 2.) 0.0 231 contains 3 significant figures 3.) M = V x D = 85.0 mL x 11.35 g/ml = 965 g (multiplication, volume contains only 3 sig figs) Question 6

Describe each material below as an element, compound, solution or heterogeneous mixture and explain your answer. 1.) Sea water 2.) Aluminum 3.) Potassium bromide 4.) Vodka 5.) Raisin bread Your Answer: 1) sea water = heterogenous mixture - when looking closely at seawater, you can sea different layers (salt, water, perhaps some other substances mixed in) 2) aluminum = element - is found on the periodic table 3) potassium bromide = compound - contains two elements found on the periodic table 4) vodka = solution - is not on the period table and contains no element names, appears as only one substance/layer 5) raisin bread = heterogeneous mixture - contains multiple substances/layers/colors when looking at it (dough, raisins, etc) Answers 1. Sea water Not on periodic table (not element) No element names (not compound) Appears to be one substance = SOLUTION 2. Aluminum Is found on periodic table = ELEMENT 3. Potassium bromide Is not on periodic table (not element) Has two element names = COMPOUND 4. Vodka Is not on periodic table (not element) No element names (not compound) Appears to be one substance = SOLUTION 5. Raisin bread Is not on periodic table (not element) No element names (not compound) Appears as more than one substance (bread, raisins) = HETEROGENOUS MIXTURE Question 7 Classify the following as physical or chemical changes: 1. A pile of leaves is burned 2. Your hair is trimmed by a hairstylist

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3. Flour, water, eggs, butter and sugar are combined and baked to make a cake Your Answer: 1. chemical change 2. physical change 3. chemical change 1. A pile of leaves is burned = Chemical 2. Your hair is trimmed by a hairstylist (hair is still hair but shorter) = Physical 3. Flour, water, eggs, butter and sugar are combined (Physical) and baked to make a cake = Chemical Question 8 Name the following compounds: 1.) Fe(OH) 3 ____________________ 2.) MgCO 3 ____________________ 3.) PF 5 ____________________ 4.) HNO 2 ____________________ Your Answer: 1) iron (III) hydroxide 2) magnesium carbonate 3) phosphorus pentafluoride 4) nitrous acid NAMING COMPOUNDS 1.) Fe(OH) 3 = Iron (III) hydroxide 2.) MgCO 3 = Magnesium carbonate 3.) PF 5 = Phosphorus pentafluoride 4.) HNO 2 = Nitrous acid Question 9 Write the formula for each of the following chemical compounds below and then explain your answer by referring to the prefixes or suffixes or showing charges that were used to determine the formula. 1.) Aluminum sulfide _______________ 2.) Lead (IV) oxide _______________ 3.) Calcium cyanide _______________ 4.) Dinitrogen Trioxide _______________ 5.) Potassium bromide _______________ Your Answer: 1) Al 2 S 3

2) PbO 2 3) Ca(CN) 2 4) N 2 O 3 5) KBr WRITING FORMULAS 1. Al +3 , S -2 = Al 2 S 3 2. Pb +4 , O -2 = PbO 2 (need just 2 Os to balance Pb) 3. Ca +2 , CN -1 = Ca(CN) 2 4. Di-two N, Tri-three O = N 2 O 3 5. K +1 , Br -1 = KBr