1) A sample of gold has a mass of 295.0 lb and a volume of 0.2446 ft3. What is i

Question

  1) A sample of gold has a mass of 295.0 lb and a volume of 0.2446 ft3. What is its specific gravity?

   B)  What are the units of specific gravity?

   C) A sample of metal has a mass of 17.40 g, and a volume of 6.31 mL. What is the density of this metal?

   D) If your front lawn is 25.0 feet wide and 20.0 feet long, and each square foot of lawn accumulates 1250 new snow flakes every minute, how much snow (in kilograms) accumulates on your lawn per hour? Assume an average snow flake has a mass of 1.50 mg.

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E) Occupational Safety and Health Administration has set the limit on the maximum percentage of carbon dioxide (CO2) in air a worker can breathe at 0.500% by mole. If dry ice (solid CO2) is sublimating (becoming a gas) in a room at a rate of 0.510 mol/min, what is the minimum rate that fresh air has to be supplied to the room so that the concentration of CO2 in the room doesn't exceed 0.500% by mole? Assume the room is well mixed, and the volume of the solid dry ice does not change.

F)  What is the percent by mass of oxygen in a gaseous mixture whose molar composition is 0.500% CO2 and 99.500% air? The composition of air is 21% mole O2, 79% mole N2, and has an average molar mass of 29.0 g/mol.

Explanation / Answer

How heavy is a gold bar? In the movies, how easily do they show someone handling a bar of gold? Should you be able to pick it up easily? How many gold bars do you think you can carry? In this exercise, you will calculate the weight in pounds of a gold bar. Densities of Common Elements and Compounds Substance Density grams per mL or cc Water 1.00 Aluminum, Al 2.70 Iron, Fe 7.80 Gold, Au 19.30 Mercury, Hg 13.5 Mathematical Definition of Density The formal definition of density is mass per unit volume. Usually the density is expressed in grams per mL or cc. Mathematically a "per" statement is translated as a division. cc is a cubic centimeter and is equal to a mL Therefore, Density = mass = g/mL volume Example: How heavy in pounds is a gold bar pictured on the right. The dimensions of gold bars held in Federal Reserve Banks is: 7 x 3.625 x 1.75 inches Solution: First, convert the measurements in centimeters. 1 inch = 2.54 cm 7 inches x 2.54 cm = 17.78 cm 1 inch Similarly, 3.625 in = 9.21 cm; 1.75 in = 4.45 cm Find the volume of the gold bars in cubic centimeters Volume = 17.76 cm x 9.21 cm x 4.45 cm = 727.9 cc Calculate the weight of the gold bar using the density of gold, which is: 19.3 g/cc Use the density as a conversion factor: 19.3 g = 1 cc 727.9 cc x 19.3 g = 14,048 g 1 cc Convert from grams to pounds. 1 lb = 454 g 14,048 g x 1 lb = 30.94 lb 454 g So the next time you see gold bars in the movies, look to see how easily they appear to pick them up. Thirty pounds is a good amount of weight that is not casually picked up.

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