F10Q1W2 - CHEM 0110 Golde QUIZ 1 WEEK 2 TUESDAY 8:00 AM...

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CHEM 0110 QUIZ 1 WEEK 2 TUESDAY 8:00 AM Golde September 7, 2010 NAME_______________________________________________________________________ 1. Evaluate the following expression: 319 + -4 -7 4.72 x 10 5.57 x 10 Give your answer to the appropriate number of sig. figs. State the number of sig. figs. and explain how you decided how many sig. figs. to use. 2. In a fast tennis serve, the ball travels at a speed of 125 mph. How long would the ball take to travel a distance of 25 meters (about 80 feet) at this constant speed? Show your work. Does your answer make sense? Give your reasoning. 1 mile = 1.609km ANSWERS 1. The division yields 847.4056, which should be rounded to 3 sig figs, 847, because each number has 3 sig. figs. Then: 847 + 319 = 1166. In the summation, all the digits before the decimal point are significant. So the answer has 4 sig. figs. 2. (Any valid approach is acceptable). Let's convert 125 mile/hr to m/s. Speed = 1km 1000m x mile 1 1.609km x 3600s hr 1 x hr 1 mile 125 = 55.87 m/s Time = 55.87m/s 25m = 0.45 s A time of about one-half second seems reasonable for a fast serve. For Make-up Only Regular recitation Day: Time: instructor: Quiz Score: Group score: Scores recorded by:
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CHEM 0110 QUIZ 1 WEEK 2 TUESDAY, 1:00 PM Golde September 7, 2010 NAME_______________________________________________________________________ 1. Evaluate the following expressions: a) 2.37 x 10 -6 + 4.5 x 10 -7 b) 7 - 6 - -8 10 x 4.5 10 x 2.37 10 x 52 . 6 + Give your answers to the appropriate number of sig. figs. State the number of sig. figs. used and explain how you decided how many sig. figs. to use. The answer to a) does NOT have 2 sig. figs. 2. We know that the energy content of carbohydrates and proteins is 4.0 Cal/g, and of fats is 9.0 Cal/g. In a certain food, 25% of the calories come from fat and the rest from carbohydrate and protein. If a serving contains 7.0g of fat, how many grams of carbohydrate + protein does this serving contain? Show your work clearly. ANSWERS 1. a) One way is to write each number with the same exponential term: 2.37 x 10 -6 + 0.45 x 10 -6 = 2.82 x 10 -6 As each number (written as x 10 -6 ) has 2 decimal places, the answer will also. This gives 3 sig. figs. for the answer. b) Using the result from (a), the division yields 2.31 x 10 -2 , which has 3 sig. figs., the same as the numerator and denominator. 2. [Accept any valid approach]. For instance: We know that fat accounts for 25% and carbohydrate + protein accounts for 75% of the calories in this food. # of fat calories in one serving = 7.0g x 9.0 Cal 1g = 63 Cal Therefore # of calories from carbohydrate + protein = 63 Cal x 75% 25% = 189 Cal Therefore mass = 189 Cal x 1g 4.0 Cal = 47g (to 2 sig. figs) For Make-up Only Regular recitation Day: Time: instructor: Quiz Score: Group score: Scores recorded by:
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CHEM 0110 QUIZ 1 WEEK 2 TUESDAY 6:00 PM Golde September 7, 2010 NAME_______________________________________________________________________ 1. Solve the following equation for y: 5(y + 3) = 2y - 6 (1 point) Describe one way in which you could check that your answer is correct. 2. A motorist was traveling 255 miles along the PA Turnpike. How much time could he save for the entire journey by driving at an average speed of 68.0 mph, instead of 65.0 mph?
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