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Chemistry I-Honors Intro Math Practice Test Answer Key For all mathematical processes, be sure to put the final answer in the correct number of sig figs. If an answer is greater than 1000 or less than 0.001, use scientific notation or points will be deducted. SHOW WORK! 1. 5 How many significant digits are in the following quantity: 0.034500 g 2. 16.4 dL 3. 212 K 55.6 fluid ounces is equivalent to how many deciliters? 55. 6 fl. oz 1 qt 946 ml 0.01 dL x ------- x --------- x ------------ = 16.437 32 oz. 1 qt. 1 ml o -77.8 on the Fahrenheit scale corresponds to what temperature on the Kelvin scale? (-77.8oF + 32) / 1.8 = -61.0oC + 273 = 212 K or -77.8oF + 459.6 = 381.8 R / 1.8 4. 5.43 x 10-32 cm3 5. 5.296 x 104 mph = 212.1 K -3 If the radius of a nucleus of an atom is only 2.35 x 10 Angstrom, what would be the 3 volume of the nucleus, in units of cm ? Assume that the nucleus is spherical. 10-10 m 102 cm o 2.35 x 10-3 A x ----------- x ---------- = 2.35 x 10-11 cm 1A 1m -32 3 3 V = 4/3 r = 5.43 x 10 cm If an object can move at a rate of 23.670 microns per nanosecond, how fast is it moving, in units of miles per hour? 23.670 m 10-6 m 10-3 km 1 mi 109 nsec 3600 sec --------------- x ---------- x ------------ x ------------ x ------------ x -----------1 nsec 1 m 1m 1.609 km 1 sec 1 hr = 5.296 x 104 mph 6. 2.5 x 103 in. 3 If a rectangular box is known to have a total volume of 56 m and the width and height of the box are known to be 1.222 yards and 77.9 cm, respectively, what is the length of the box, in units of inches? 1.222 yds(36 in. / 1 yd)(2.54 cm / 1 in.)(1 m / 100 cm) = 1.117 m 77.9 cm = 0.779 m V = (56 m3 ) / [(1.117 m)(0.779 m) = length = 64.3 m 64.3 m(100 cm / 1m)(1 in. / 2.54 cm) = 2532.85 in. 7. 6.9 g/ml A solid object that has a mass of 67.006 grams is lowered into a graduated cylinder that has 10.0 ml of distilled water in it. If the final volume reading in the graduated cylinder is 19.7 ml, what is the density of this object? D = 67.006 grams / (19.7 ml - 10.0 ml) = 6.908 g/ml -28. 3.46 A 500.0-ml flask is known to contain 2.23 grams of an inert gas. What is the specific gravity of this gas? D = 2.23 g / 0.500 liter = 4.46 g/L ; sp.gr = 4.46 g/L / 1.29 g/L = 3.46 9. 11.0 g / L What is the density of a sample of xenon hexafluoride gas at STP conditions? 245.3 g/mole x 1 mole / 22.4 L = 10.951 g L 10. 8.435 g/ml A metal block is placed on a balance and found to have a mass of 127.88 grams. The block is then suspended from a balance and totally submerged into a large beaker of distilled water. The balance reading is 112.72 grams. What is the density of this o object? Assume that the room temperature is chilly - about 4 C. buoyancy = 127.88 g - 112.72 g = 15.16 g block = 15.16 g water = 15.16 ml water = 15.16 ml volume of block displacing the water D = 127.88 g / 15.16 ml = 8.435 g/ml 11. 1.22 cm 3 A regular zinc cylinder (density = 7.13 g/cm ) has a mass of 365 grams and a length of 4.29 inches. What is the radius of this cylinder, in cm? 4.29 in (2.54 cm / 1 in.) = 10.9 cm 365 g ( 1 cm3 / 7.13 g) = 51.2 cm3 = r2h r2 = 1.496 cm2 = r = 1.223cm 12. 7.02 g/ml A density determination needs to be made of an unknown organic sample that is known to react with water, so volume displacement with water is not an option. When placed on a balance, it is found to have a mass of 17.36 grams. The sample is then suspended from a balance and totally submerged into a container of an alcohol, whose specific gravity is 2.12. The balance reading is 12.12 grams. What is the density of this object? 17.36 g - 12.12 g = 5.24 g 5.24 g ( 1 ml / 2.12 g) = 2.47 ml D = 17.36 g / 2.47 ml = 7.02 g/ml 13. 4.82 x 104 g / mole A 100.0-microliter (l) container holds a 215.00-milligram sample of a gas at STP conditions. What is the molecular weight of this gas? 0.215 g 22.4 L -------------- x --------- = 4.82 x 104 g / mole 100 x 10-6L 1 mole