(if you see any errors, please let me know!! ) KEY Honors Chemistry Assignment Sheet- Unit 2

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1 (if you see any errors, please let me know!! ) KEY Honors Chemistry Assignment Sheet- Unit 2 Learning Objectives: 1. Relate the ideas of precision and accuracy to measurements & significant figures. 2. Be able to add, subtract, multiply, and divide using significant figures. 3. Be able to perform advanced dimensional analysis problems (including common metric conversions) 4. Be able to perform advanced density calculations. Assignments (Due day before Unit 2 Test) 1. Precision, Accuracy, & Sig Figs See below 2. Dimensional Analysis See below 3. Advanced Density Related Calculations See below Honors Assign #1-Precision, Accuracy, & Significant Figures 1. a) Explain the difference between precision and accuracy when it comes to a measurement. Accuracy - An indication of how close a measurement is to the true value Precision - An indication of the scale on the measuring device that was used In other words, the more correct a measurement is, the more accurate it is. On the other hand, the smaller the scale on the measuring instrument, the more precise the measurement. b) How do significant figures relate to precision/ & or accuracy in a measurement? In order to determine the precision of a measurement, we need to merely look at its significant figures. If two instruments measure the same thing, the one which gives you a significant figure in the smallest decimal place is the more precise instrument. Use the correct number of sig figs in your answers, make sure to review the rules = = = = x = = x (this has a mix of subtraction and division, with different rules. You must do them separately = 2.2 w/ one decimal place. Then divide 2.2 by 1.58, the answer is 1.4 w/ 2 sig figs.)

2 = 9. The following are placed in a beaker weighing g: g Nacl, g of sand, & 5.0 g H 2 O. What is the final mass of the beaker? g 10. If the beaker containing a sample of alcohol weighs g & the empty beaker weights g, what is the weight of the alcohol? g

3 Honors Assign #2-Advanced Dimensional Analysis You must use dimensional analysis, show your work, and use the correct number of sig figs. Box in answers! 1. Eggs are shipped from a poultry farm in trucks. The eggs are packed in cartons of one dozen eggs each; cartons are placed in crates that hold 20 cartons each. The crates are stacked in the trucks, 5 crates across, 25 crates deep and 25 crates high. How many eggs are in 5 truckloads? 5 Truck Loads 3125 Crates 20 Cartons 12 Eggs 1 Truckload 1 Crate 1 Carton = 3,750,000 4,000,000 Eggs or 4x How many miles could you drive for $7.90 if the gas mileage of your car is 14 km/liter of gas and the price is $1.29/gal? (1.61 km/mile, 4 qt/gal, 1.1 qt/l) Dollars 1 Gallon 4 qt 1 L 14 km 1 Mile 1.29 Dollars 1 Gallon 1.1 qt 1 L 1.61 km = Miles 3. David Hill operates a crane that can pick up 3.0 tons of excavated earth in an hour. Dave s wages are $35 per hour. What, then, is the cost of picking up 85 kg of excavated earth? (2.2 lb/kg, 2000 lb/ton) 85 kg 2.2 lb 1 ton 1 hour 35 Dollars 6545 = $1.09 $ kg 2000 lb 3 ton 1 hr 4. Each liter of air has a mass of 1.80 grams. How many liters of air are contained in 2.5 x Kg of air? 2.5x g 1 L 1.388x x kg 1.80g mole of Si contains 6.02 x atoms x atoms of Si have a mass of grams. How many atoms of Si are contained in a computer chip that has a mass of mg? (Assume the entire chip is Si) mg 1g 1 mole 6.02x10 23 atoms 1000 mg 28.1g 1 mol = 2.349x10 25 = 8.359x10 20 (Error on original posting see this one!) 28100

4 6. Convert 8.3 liters into teaspoons. (1tsp= 15 ml) = tsps 8.3 L 1000ml 1tsp 1 L 15mL 7. Convert 3.1 x 10 4 Km into yards. (1 m = yards) 3.1x10 4 km 1000m yds 1km 1m = 3.391x x10 7 yds 8. Thomas Jefferson developed his own system of measurement using decimal notation (which was never adopted in the US). In Jefferson s system, 10 inches = 1 foot; 10 feet = 1 decad; 10 decads = 1 rood; 10 roods = 1 furlong. Use Jeffereson s system to convert 1150 km into furlongs. (Also, 1 inch = 2.54 cm) 1150km 1000m 100cm 1in 1 foot 1 decad 1 rood s 1 furlong 1km 1m 2.54cm 10 in 10 ft 10 decad 10 roods = Furlongs

5 Honors Assign. #3- Density Calculations Directions: Show ALL work in order to receive credit. Pay attention to units and sig figs at all time. 1. A block occupies ft 3. What is the volume in mm 3? (1 inch = 2.54 cm).2487ft inch cm mm ft inch cm 3 = 7.326x10 6 mm 3 2. A graduated cylinder is placed on an electronic balance, and the scale reads grams ml of glycerine are added, and the scale reads grams. What is the density of glycerine? 91.78g 78.32g = 13.46g D= 13.46g D= 1.35g/mL 10.0mL 3. A sample of a gas has a volume of 4.0 L and a mass of g. What is its density in g/cm 3? 4.0 L 1000mL 1cm 3 1 L 1 ml Volume = 4000cm 3 4.0x10 3 cm 3 Density= 4.922g = g/cm 3 or 1.2x10-3 g/cm 3 4.0x10 3 cm 3 4. A cylinder contains water to a level of 15.5 ml moles of copper are dropped in. What will be the new height of the water. Copper s density is 8.96 g/ ml Moles Cu 63.55g 1 mole Cu = 3g Cu 8.96g/mL = 3g V= 0.3mL 15.5mL +.3 = 15.8mL V 5. The density of aluminum is 2.70 g/cm 3. Calculate the number of aluminum atoms in a piece of foil that is 2.0 cm x 3.1 cm x 2.6 cm. 2.0 x 3.1 x 2.6 = 16.12cm g/cm 3 = m m = 43.5 g 16.12cm g Al 1 mole 6.02x10 23 atoms 26.98g 1 mole = 9.7x10 23 atoms

6 6. What is the mass in g of 25 ml of oxygen gas if it s density is 1.43 g/l? 15mL 1L 1000mL =.025 L 1.43g/L = m m = 0.036g.025 L 7. A student determines the mass and volume of3 samples of a liquid to be: Sample Volume Mass Density - Determine the density (record in table) A 116 ml 85 g.73 g/ml Could all of these be samples of the same B 168 ml 101 g.60g/ml substance? If not, which could be? C 158 ml 115 g.73 g/ml a + c could be same substance - 8. A gas is confined in a rectangular tank 25.0 cm long, 8.0 cm high and 10.4 cm wide. If the density of the gas is 19.3 g/l, what is the mass of the gas? 25.0 cm x 8.0 cm x 10.4 cm = 2080 cm cm 3 1mL 1cm 3 = 2080mL 2080mL 1L 1000mL = 2.08 L 19.3 g/l = g g = 40.g 2.08L 9. If the density of an object is 2.87 x 10-4 lbs/inch 3, what is the density in g/ ml? (1 inch = 2.54 cm, 1 Lb = 454 g) 2.87x10-4 lbs 454g 1 3 inch 3 Inch 3 1lb cm 3 = 7.95x10-3 g/ml

7 10. The density of aluminum is 2.70 g/cm 3. Express the value in kg/ m g 1kg cm Cm g 1 3 cm 3 = x10 3 kg/m 3