CH1010 Lecture 2

10g nowyoucandispenseviasyringe sampleproblems

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Unformatted text preview: ions with Density Need 1.10 gram of toluene (toluene is a liquid) Density of toluene = 0.867 g/cm3 = 0.867g/mL 1.10 grams toluene x 1mL = 1.268mL 0.867g Correct to 3 significant figures Answer: 1.27mL toluene needed to give 1.10 g Now you can dispense via syringe Sample Problems Sample Problems Sample Problem 1.3 Converting Units of Length PROBLEM: To wire your stereo equipment, you need 325 centimeters (cm) of speaker wire that sells for $0.15/ft. What is the price of the wire? PLAN: Known ­ length (in cm) of wire and cost per length ($/ft) We have to convert cm to inches and inches to feet followed by finding the cost for the length in ft. length (cm) of wire 2.54 cm = 1 in length (in) of wire 12 in = 1 ft length (ft) of wire 1 ft = $0.15 Price ($) of wire SOLUTION: Length (in) = length (cm) x conversion factor = 325 cm x in = 128 in 2.54 cm Length (ft) = length (in) x conversion factor ft = 10.7 ft 12 in Price ($) = length (ft) x conversion factor = 10.7 ft x $0.15 ft = $1.60 = 128 in x Sample Problem 1.4 Converting Units of Volume PROBLEM: When a small piece of galena, an ore of lead, is submerged in the water of a graduated cylinder that originally reads 19.9 mL, the volume increases to 24.5 mL. What is the volume of the piece of galena in cm3 and in L? PLAN: The volume of galena is equal to the change in the water volume before and after submerging the solid. volume (mL) before and after addition subtract volume (mL) of galena 1 mL = 1 cm3 volume (cm3) of galena SOLUTION: 1 mL = 10­3 L volume (L) of galena (24.5 ­ 19.9) mL = volume of galena = 4.6 mL 3 4.6 mL x 1 cm mL = 4.6 cm 3 4.6 mL x 10 L mL ­3 = 4.6x10­3 L Sample Problem 1.5 Converting Units of Mass PROBLEM: What is the total mass (in kg) of a cable made of six strands of optical fiber, each long enough to link New York and Paris (8.84 x 103 km)? One strand of optical fiber used to traverse the ocean floor weighs 1.19 x 10­3 lbs/m. length (km) of fiber PLAN: The sequence of steps may vary but essenti...
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