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UT Arlington CHEM 1441 - Exam 1 Study Guide

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CHEM 1441 1st EditionExam # 1 Study Guide Lectures: 1 - 7Lecture 1 (January 23) Chapter 1: Keys to Study of ChemistrySignificant Figures [SIG FIG PROBLEMS WILL BE ON TEST] What is an exact number and what is an inexact number?Exact Numbers – include counting numbers, average number of terms, and defined measurements. Have infinite number of sig figs. For Example: 3 pens, 1 in = 2.54 cm, 1000g = 1kgInexact Numbers – include numbers that are not exact and have uncertainty, such as measurements taken in a lab using equipment like a beaker, graduated cylinder, etc. For Example: 1kg≈ 2.205lb, 1 mile = 1.609km Counting Sig FigsAll non-zero digits are significant. For Example: 5.32 (3 sig figs), 4.4 (2 sig figs), 35.52 (4 sig figs), 0.65 (2 sig figs)All zeros between other significant figures are significant. For Example: 5.002 (4 sig figs)Leading zeros are not significant. For Example: 0.045 (2 sig figs), 0.306 (3 sig figs)Trailing zeros are always included if decimal is present. For Example: 0.003040 (4 sig figs), 150 (2 sig figs), 150. (3 sig figs), 150.10 (5 sig figs)Scientific notation helps remove ambiguity (by using a decimal point). For Example: 150 turns into… 1.50 x 103 (3 sig figs), 1.5 x 103 (2 sig figs) Calculations using Significant FiguresAddition and Subtraction (look for least precise term / find the common significant decimal place for all terms) For Example: 29.52 + 3.001 + 7219.5 = ? Line them up by the decimal point 29.52 3.001 Answer is 7251.0 (5 sig figs) or Least precise # +7219.5 7.2510 x 103 7251.021 25.57 g – 25.49 g = ? 25.57 +25.49 Answer is 00.08 g (1 sig fig) or 8. x 10-2 g 00.08 5.68 + 8.3 = ? 5.68+8.3 Answer is 14.0 (3 sig figs) or 1.40 x 101 13.98 ≈ 14.0need to round off to least precise term Multiplication and Division (use smallest number amount of sig figs) For Example: 2.99 x 7.3 = ?Count number of sig figs in each term 3 sig figs x 2 sig figs = answer with 2 sig figs 2.99 x 7.3 = 21.827 round off to 2 sig figs Answer is 22. Or 2.2 x 101 5.982 x 0.00201 = ? 4 sig figs x 3 sig figs = answer with 3 sig figs 5.982 x 0.00201 = 12.02382 Answer is 12.0 or 1.2 x 101 Mixed Operations For Example: 12.3/8.72 + 295.767 = ? mark the sig fig Use PEMDAS (do mul/div first, then add/sub) 1.4105505 + 295.767 = 1.4105505 use least precise term Don’t round off until the end, + 295.767 keep track of sig figs by marking them. 297.1775504 5 sig figs in answer Answer is 297.18 or 2.9718 x 102 Lecture 2 (January 26)Chapter 1: Keys to Study of Chemistry cont’d Significant Figure Concept Check:(31.49 – 12.) x (434.049 – 432.1) = ?(19.49) x (1.949) = 37.986012 sig fig 2 sig fig ans with 2 sig figAnswer is 38. or 3.8 x 101 Doing Dimensional Analysis Step 1) Write down what you know. Step 2) Start with the given measured quantity. Step 3) Apply conversion factors. MEMORIZE THESE 1in = 2.54cm, 1kg = 2.205, 1ml = 1cm3, 12in = 1ft, 1000g = 1kg For Example: How many feet are in 6.0 yds?Step 1) 1yd = 3 ft (this is an exact measurement, so it has infinite sig figs)Step 2 + 3) 6.0 yds x 3 ft = 18. ft 1 yd  Know the SI Unit System, CGS System and Metric Prefixes SI Unit System Mass: kg (kilograms) Volume: volume is a combined unit (l*h*w*) -m3 (meters cubed) or area – m2(metersLength: m (meters) squared) Temperature: K (Kelvin) Time: s (seconds)Chemistry (CGS System) Mass: g (grams) Volume: L (liters) Length: cm; m (centimeters; meters) Temp: K Time: sMetric Prefix Table [MEMORIZE] Power always belongs to the base unit (g,s,L,m) deci; 1 dg = 1x10-1 g 1x101 g = 1 Dg; Deca centi; 1 cg = 1x10-2 g 1x102 g = 1 hg; hecta milli; 1 mg = 1x10-3 g 1x103 g = 1 kg; kilo micro; 1 µg = 1x10-6 g 1x106 g = 1 Mg; Mega nano; 1 ng = 1x10-9 g 1x109 g = 1 Gg; Giga pico; 1 pg = 1x10-12 g 1x1012 g = 1 Tg; Tera femto; 1 fg = 1x10-15 g 1x1015 g = 1 Pg; Peta Conversion ProblemsConvert 0.00275 dL to µL. Step 1) 1 dL = 1 x 101 L, 1 µL = 1 x 10-6 LStep 2+3) 0.00275 dL x 1x101 L x 1 µL = 275. µL 1 dL 1x10-6 LExpress 65. miles/hour in m/s. Step 1) 1 mile = 1.609km, 1 hr = 60 min, 1 min = 60 s, 1 km = 1x103 mStep 2+3) 65. miles x 1.609 km x 1x103 m x 1 hr x 1 min = 29. m/s 1 hr 1 mile 1 km 60 min 60 sExpress the density 13.6 g/mL in lbs/ft3 . (Hint: this may be on test) Step 1) 2.205 lb = 1 kg, 1 kg = 1x103 g, 1 mL = 1 cm3, 1 ft = 12 in, 1 in = 2.54 cmStep 2+3) 13.6 g x 1 mL x


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