Chapter COURSE NAME: CHEMISTRY 101 COURSE CODE:

Transcription

1 Chapter 1 COURSE NAME: CHEMISTRY 101 COURSE CODE:

2 Chapter 1 2

3 International System of Units (SI) Science problem solving requires both: Metric system English system 3

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5 Volume SI derived unit for volume is cubic meter (m 3 ) 1 cm 3 = (1 x 10-2 m) 3 = 1 x 10-6 m 3 1 dm 3 = (1 x 10-1 m) 3 = 1 x 10-3 m 3 1 L = 1000 ml = 1000 cm 3 = 1 dm 3 1 ml = 1 cm 3 5

6 Density SI derived unit for density is kg/m 3 density = 1 g/cm 3 = 1 g/ml = 1000 kg/m 3 mass volume d = m V A piece of platinum metal with a density of 21.5 g/cm 3 has a volume of 4.49 cm 3. What is its mass? d = m V m = d x V = 21.5 g/cm 3 x 4.49 cm 3 = 96.5 g 6

7 A Comparison of Temperature Scales K = 0 C K = 0 0 C 373 K = C 0 F = 9 x 0 C F = 0 0 C F = C 7 6

8 Convert F to degrees Celsius F = 9 5 x 0 C F 32 = 9 5 x 0 C x ( 0 F 32) = 0 C 0 C = 5 x ( 0 F 32) 9 0 C = 5 x ( ) =

9 Scientific Notation The number of atoms in 12 g of carbon: 602,200,000,000,000,000,000, x The mass of a single carbon atom in grams: x N x 10 n N is a number between 1 and 10 n is a positive or 8 negative integer

10 Any digit that is not zero is significant kg 4 significant figures Zeros between nonzero digits are significant 606 m 3 significant figures Significant Figures Zeros to the left of the first nonzero digit are not significant 0.08 L 1 significant figure If a number is greater than 1, then all zeros to the right of the decimal point are significant 2.0 mg 2 significant figures If a number is less than 1, then only the zeros that are at the end and in the middle of the number are significant g 3 significant figures 9

11 How many significant figures are in each of the following measurements? 24 ml 2 significant figures 3001 g 4 significant figures m 3 3 significant figures 6.4 x 10 4 molecules 2 significant figures 560 kg 2 significant figures 10

12 Addition or Subtraction Significant Figures The answer cannot have more digits to the right of the decimal point than any of the original numbers one significant figure after decimal point round off to two significant figures after decimal point round off to

13 Multiplication or Division Significant Figures The number of significant figures in the result is set by the original number that has the smallest number of significant figures 4.51 x = = sig figs round to 3 sig figs = = sig figs round to 2 sig figs 12

14 Exact Numbers Significant Figures Numbers from definitions or numbers of objects are considered to have an infinite number of significant figures The average of three measured lengths; 6.64, 6.68 and 6.70? = = = 7 Because 3 is an exact number 13

15 Accuracy how close a measurement is to the true value Precision how close a set of measurements are to each other accurate & precise precise but not accurate not accurate & not precise 14

16 Dimensional Analysis Method of Solving Problems Determine which unit conversion factor(s) are needed Carry units through calculation.2 If all units cancel except for the desired unit(s), then the problem was solved correctly..1.3 given quantity x conversion factor = desired quantity given unit x desired unit given unit = desired unit 15

17 Dimensional Analysis Method of Solving Problems How many ml are in 1.63 L? Conversion Unit 1 L = 1000 ml 1000 ml 1.63 L x = 1630 ml 1L 1L 1.63 L x = ml L 2 ml 16

18 Question 1 Which of the following is an example of a physical property? A) combustibility D) density E) A and D B) corrosiveness C) explosiveness Question 3 Convert 240 K and 468 K to the Celsius scale. A) 513 o C and 741 o C B) -59 o C and 351 o C C) o C and 108 o C D) -33 o C and 195 o C Question 2 Which of the following represents the greatest mass? A) 2.0 x 10 3 mg B) 10.0 dg C) kg D) 1.0 x 10 6 μg E) 3.0 x pg Question 4 Calculate the volume occupied by 4.50 X 10 2 gold (density = 19.3 g/cm 3 ). A) 23.3 cm 3 B) 8.69 x 10 3 cm C) 19.3 cm 3 g of D) 450 cm 3 17

19 Question 5 The melting point of bromine is -7 o C. What is this melting point expressed in o F? A) 45 o F B) -28 o F C) -13 o F D) 19 o F E) None of these is within 3 o F of the correct answer. Question 7 How many significant figures should you report as the sum of ? A) 3 B) 5 C) 7 D) 6 E) 4 Question 6 How many significant figures are there in the measurement g? A) 6 B) 5 C) 4 D) 3 19 E) 2 18

20 Question 8 Walking fast can consume 5.0 kcal per minute. How many hours of exercise are required to consume 450 kcal, the energy in a large candy bar? A) 7.5 hr B) 1.25 hr C) 1.75 hr D) 1.5 hr E) 1 hr Question 10 A bar of gold is measured with the ruler shown. The length of the bar should be reported as: A) 3 cm B) 3.0 cm C) 2.7 cm D) 2 cm Question 9 Together, Americans drive about 5.0 x 10 9 miles per day, and their cars get an average of 22 miles per gallon of gas used. For each kilogram of gasoline used, about 3 kg of carbon dioxide is produced. How many kilograms of CO 2 are emitted into the atmosphere by cars in the US each day? [1 gal = 3.5 kg] A) 2 x 10 9 kg B) 2.4 x 10 9 kg C) 8.3 x 10 9 kg D) 1.6 x 10 9 kg E) None of the above 19

21 Question 14 What is the SI unit of mass? A) Meter C) Gram B) Centimeter D) Kilogram (kg) Question 15 Which is a useful equivalent? A) 1 liter = 1 decimeter cubed B) 1 meter = 1 centimeter cubed C) 1 cubic centimeter = 1 cubic decimeter D) 1 kilogram = 1 liter 21 20

22 Question 16 Which of the following is true about the scientific method? A) A hypothesis is a set of observations that are explained by an experiment. B) Researchers design experiments to prove the conclusions they have already reached. C) The purpose of performing an experiment is to confirm or contradict a hypothesis. D) To be useful, data must be qualitative. E) Quantitative data are usually in the form of descriptive observations. Question 18 A 9.4-g sample of powdered titanium was added to a graduated cylinder originally containing 6.8 ml of water. After addition of the titanium, the water level in the graduated cylinder was 8.9 ml. What is the density of titanium? A) 1.4 g/cm 3 B) 4.5 g/cm 3 C) 1.1 g/cm 3 D) 0.22 g/cm 3 Question 17 Which of the following is not an example of a mixture? A) iced tea 22 B) distilled water C) mashed potatoes D) vegetable soup E) tomato juice Question 19 At one atmosphere pressure, mercury solidifies at o F. Express this temperature in degrees Celsius and Kelvin. A) -126 o C and 147 K B) -39 o C and 234 K C) -21 o C and 252 K D) 39 o C and 312 K E) -68 o C and 205 K 21

23 Question 20 How many significant figures are there in the number g? A) 8 B) 7 C) 6 D) 5 Question 21 A sample of a liquid has a density of 2.1 g/ml. What volume of the liquid has a mass of g? A) 8.9 ml B) 2.0 ml C) 2.02 ml E) 0.50 ml D) ml Question 22 A laboratory technician analyzed a sample three times for percent iron and got the following results: 22.43% Fe, 24.98% Fe, and 21.02% Fe. The actual percent iron in the sample was 22.81%. The analyst's A) precision was poor but the average result was accurate. B) accuracy was poor but the precision was good. C) work was only qualitative. D) work was precise. E) C and D. Question 23 The density of magnesium is 1.7 g/cm 3, and the density of iron is 7.9 g/cm 3. Consider a block of iron with a mass of 819 g. What is the mass of a block of magnesium that has the same volume as the block of iron? A) 1.8 x 10 2 g B) 61 g C) 2.8 x 10 3 g 23 D) 3.8 x 10 3 g E) None of the above. 22

24 Question 24 The recommended daily allowance (RDA) of calcium is 1200 mg. Calcium carbonate contains 12% calcium by mass. How many grams of calcium carbonate are needed to provide the RDA of calcium? A) 1.3 g B) 1.4 g C) 0.14 g D) 10. g E) 0.19 g Question 25 Table salt (sodium chloride) is 42.7% sodium. How many grams of salt contain 76.0 g of sodium? A) 32.5 g B) 178 g C) 3.25 x 10 3 g E) 1.78 x 10 4 g D) 1.78 g 26. Which of the following is a measurement of mass in the metric system? A) Celsius B) centimeter C) milliliter D) kilogram E) meter A 27. A value of 25 C is a measurement of A) density. B) distance. C) mass. D) volume. E) temperature. 28. A value of 36 ml is a measure of A) distance B) density C) temperature E) volume D) mass 23

25 29. value of 345 mm is a measure of A) temperature B) density C) volume D) distance E) mass 30. The measurement m, expressed correctly using scientific notation, is A) 0.43 x 10-5 m B) 4.3 x 10-6 C) 4.3 x 10-7 D) 4.3 x