Thursday, February 28, 2019

Student Life

Your examen pull up stakes be multiple cho sorbet Exam 1 foregoing Chemistry Be sure to show your set up for e precise(prenominal) mathematical problems. Your firmness of purposes essential devote the reclaim tot up of signifi force outt digits and the fall off unit of measurements. I. Chemistry is a quantitative science therefore we must befuddle measurements. All measurements have an uncertainty that we submit to be aw atomic number 18 of in our calculations. A. We need to be able to determine the number of signifi providet figures in a measurement. For the sp be-time activity measurement state the number of signifi behindt figures. (4pts) 1. 1. 000 cm 2. 2. 590 x 10-5 m 4 3. . 020 g 4. 1000 cm 2 1 B. We need to be able to add, subtract, multiply, and divide with measurements. adjudicate the pursuit problems. (4 pts) 1. 3. 02 cm + 5 cm + 0. 002 cm = 8 cm 3. 2. 0 cm x 2. 00 cm x 2. 000 cm = 8. 0 cm3 2. 5. 35 g 0. 005 g = 5. 35 g 4. 7. 89 g / 5. 2 mL = 1. 5 g/mL B. It is oft necessary to turn from one unit to another. This is easily accomplished with the right unit factor. Solve the following problems. 1. During the pop off six lunar landings 842 pounds of Moon samples have been collected. What is this plenteousness expressed in kilograms? ( 2. pounds = 1 kilograms) (4 pts) 842 lbs x 1 kg / 2. 2 lbs = 382. 7272727 kg = 380 kg 2. If a 250 mL beaker weighs 95. 4 g, what is the dope in kilograms? (4 pts) 95. 4 g x 1kg / 1000g = 0. 0954 kg = 9. 54 x 10-3 kg 3. If the radius of an group O atom is 6. 6 x 10 (5 pts) 6. 6 x 10 10 dm x 1 m / 10 dm x 109 nm/ 1 m = 6. 6 x 10-2 nm -10 dm, what is the radius in nm? 1 C. Chemists often deal with pct problems. As long as you remember that share refers to per 100, these problems can be solved. 1. A penny minted after 1982 is composed of squealer and zinc only. If a penny has a mass of 2. 07 g and is 2. 50 % copper. What is the mass of zinc in the coin? (5 pts) 2. 507 g x 2. 50/100 = 0. 062675 g of Cu 2. 507 g of penny 0. 062675 g of Cu = 2. 444325 g = 2. 444 g of Zn (2. 44 g of Zn is correct also) D. Density is a very important concept for chemist. The meanness of a substance can be obtained in a chemistry laboratory. 1. A good-for-naught male plug with a mass of 23. 75 g is dropped in a 50-mL gradatory cylinder that has 20. 4 mL of water. After the s altitudeper is dropped in the receive cylinder, the water level rises to 24. 7 mL. What is the parsimoniousness of the rubber cud? 5 pts) 2. 375 g / (24. 7 mL 20. 4 mL) = 5. 523255814 g / mL = 5. 52 g / mL (5. 5 g /mL is accepted) We can play predictions if the compactness is known. 2. A glass cylinder contains quaternary liquid layers mercury (d = 13. 6 g/mL), chloro attain (d = 1. 49 g/mL), water (d = 1. 00 g/mL), ether (d = 0. 708 g/mL). If a piece of ice (d = 0. 917 g/mL) is dropped into the cylinder, where does it recognize to rest? Why? (5 pts) The mercury layer lead be on the bottom, then the chloroform, then the water, and finally the ether. The ice will sink in the ether layer and float on top of the water layer.If the tightfistedness is know, we can we can find the mass of a given peck or the hoi polloi of a given mass. 3. The density of aluminum is 2. 70 g/mL. What volume will 250 g of Al occupy? What is the mass of a piece of aluminum with a volume of 250 mL? (6 pts) 250 g of Al x 1 mL / 2. 70 g = 92. 59259259 mL = 93 mL 250 mL of Al x 2. 70 g / 1 mL = 675 g = 680 g 2 Using the density value we can indirectly obtain distances that are too nonaged to measure directly. 4. A sample of aluminum stupefy has a length of 10. 0 cm and a width of 5. 7 cm. If the aluminum mollycoddle weighs 0. 234 g, what is the thickness of the aluminum foil?Remember that the density of aluminum is 2. 70 g/mL. (6 pts) Volume of Al = length x width x thickness = mass / density 0. 234 g x 1 mL / 2. 70 g = 0. 0866666666 mL 0. 086666666 mL / 10. 0 cm x 5. 7 cm = 0. 001520467 cm = 1. 5 x 10 3 cm E. Heat a nd temperature are cardinal very important concepts. 1. In your own words, please state the difference amidst rage and temperature. What is a common unit of each? (5 pts) Heat measures the keep drink energy of a sample and temperature measure the intensity of foment or the average heat of a sample. A common unit of heat is a large calorie and a common unit of temperature is Kelvin.It is important to be able to transfer from one temperature unit to another. 2. Aluminum melts at 1220 F. (You can see why aluminum is not a liquid at room temperature) What is the thawing point of aluminum in degree Celsius ( C) and in Kelvin o C (6 pts) (K)? (oF 32 oF) x 100 oC = clxxx oF (1220 oF 32)(100 / 180) = 660 oC 660 oC + 273 = 933 K o o 3. launch the ions present and their relative numbers racket in kelvin sulfate. a) b) c) d) e) 1K+ and 1 SO42K+ and 1 SO321K+ and 2 SO422K+ and 1 SO423K+ and 1 SO43- 3 4. How numerous cm2 are in an area of 4. 21in2? a. b. c. d. e. 10. 7 cm2 114 cm2 27. cm2 1. 66 cm2 1. 14 cm2 5. In performing a multistep calculation, when should you rophy off the reception in the computing device display? (5 pts) In a multistep calculation you should round off the answer at the end of the calculation E. Matter and Energy. 1. We intimate four legal injury in chapter 4, heterogeneous form, homogeneous assortment, compound, and element. Please an pillow slip of each. (8 pts) An caseful of a heterogeneous mixture is the earths crust. A heterogeneous mixture can be separated into pure substances by sensual methods. An example of a homogeneous mixture is salt water.The properties of a homogeneous mixture constant for a given sample. An example of a compound is NaCl. A compound can be broken down into elements by unexceptional chemic responses. An example of an element is Na. An element is a substance that can not be broken down still by a chemical reaction. 2. Match Symbols and Names (10 pts) 1. atomic number 11 2. weigh 3. carbon 4 . nitrogen 5. phosphorous d c e b a a. P b. N c. Fe d. Na e. C 4 1. Cl 2. Ce 3. Cu 4. Co 5. Ca e c b d a a. Calcium b. Copper c. Cesium d. conscientious objector e. Chlorine 3. Give an example for each of the following terms (8 pts) a. hysical stead Appearance, melting point, stewing point, density, heat and electrical conductivity, solubility, and physical state downstairs normal conditions are all examples of physical properties. b. chemical keeping A chemical property of a substance describes its chemical reactions with other substances. The chemical property of sodium states that sodium will react with water to form hydrogen gas. c. physical channelize A physical change include changing shape, volume, or physical state. For example when water changes to ice. d. chemical change A chemical change always involves the formation of a radical substance.Gas bubbles from the reaction of calcium with water. Fill in the blanks of the following hedge Symbol number of protons number of neutrons number of electrons mass number 37 Cl17 20 18 48 Cr3+ 24 24 21 24 Mg 12 12 12 37 48 24 Might not be on test. Ask teacher. Chlorine has both stable isotopes with hoi polloi of 34. 97 amu and 36. 97 amu. What is the relative abundance of the two isotopes? a. b. c. d. e. 50. 00% 35Cl and 50. 00 % 37Cl 35. 45% 35Cl and 64. 55 % 37Cl 64. 55% 35Cl and 35. 45% 37Cl 24. 23% 35Cl and 75. 77 % 37Cl 75. 77 % 35Cl and 24. 23 % 37Cl 5Student LifeYour exam will be multiple choice Exam 1 Introductory Chemistry Be sure to show your set up for all mathematical problems. Your answers must have the correct number of significant digits and the correct units. I. Chemistry is a quantitative science therefore we must make measurements. All measurements have an uncertainty that we need to be aware of in our calculations. A. We need to be able to determine the number of significant figures in a measurement. For the following measurement state the number of significant figures. (4pts) 1 . 1. 000 cm 2. 2. 590 x 10-5 m 4 3. . 020 g 4. 1000 cm 2 1 B. We need to be able to add, subtract, multiply, and divide with measurements. Solve the following problems. (4 pts) 1. 3. 02 cm + 5 cm + 0. 002 cm = 8 cm 3. 2. 0 cm x 2. 00 cm x 2. 000 cm = 8. 0 cm3 2. 5. 35 g 0. 005 g = 5. 35 g 4. 7. 89 g / 5. 2 mL = 1. 5 g/mL B. It is often necessary to convert from one unit to another. This is easily accomplished with the right unit factor. Solve the following problems. 1. During the last six lunar landings 842 pounds of Moon samples have been collected. What is this mass expressed in kilograms? ( 2. pounds = 1 kilograms) (4 pts) 842 lbs x 1 kg / 2. 2 lbs = 382. 7272727 kg = 380 kg 2. If a 250 mL beaker weighs 95. 4 g, what is the mass in kilograms? (4 pts) 95. 4 g x 1kg / 1000g = 0. 0954 kg = 9. 54 x 10-3 kg 3. If the radius of an oxygen atom is 6. 6 x 10 (5 pts) 6. 6 x 10 10 dm x 1 m / 10 dm x 109 nm/ 1 m = 6. 6 x 10-2 nm -10 dm, what is the radius in nm? 1 C. Chemists often deal wit h percent problems. As long as you remember that percent refers to per 100, these problems can be solved. 1. A penny minted after 1982 is composed of copper and zinc only. If a penny has a mass of 2. 07 g and is 2. 50 % copper. What is the mass of zinc in the coin? (5 pts) 2. 507 g x 2. 50/100 = 0. 062675 g of Cu 2. 507 g of penny 0. 062675 g of Cu = 2. 444325 g = 2. 444 g of Zn (2. 44 g of Zn is correct also) D. Density is a very important concept for chemist. The density of a substance can be obtained in a chemistry laboratory. 1. A rubber stopper with a mass of 23. 75 g is dropped in a 50-mL graduated cylinder that has 20. 4 mL of water. After the stopper is dropped in the graduated cylinder, the water level rises to 24. 7 mL. What is the density of the rubber stopper? 5 pts) 2. 375 g / (24. 7 mL 20. 4 mL) = 5. 523255814 g / mL = 5. 52 g / mL (5. 5 g /mL is accepted) We can make predictions if the density is known. 2. A glass cylinder contains four liquid layers mercury (d = 13 . 6 g/mL), chloroform (d = 1. 49 g/mL), water (d = 1. 00 g/mL), ether (d = 0. 708 g/mL). If a piece of ice (d = 0. 917 g/mL) is dropped into the cylinder, where does it come to rest? Why? (5 pts) The mercury layer will be on the bottom, then the chloroform, then the water, and finally the ether. The ice will sink in the ether layer and float on top of the water layer.If the density is know, we can we can find the mass of a given volume or the volume of a given mass. 3. The density of aluminum is 2. 70 g/mL. What volume will 250 g of Al occupy? What is the mass of a piece of aluminum with a volume of 250 mL? (6 pts) 250 g of Al x 1 mL / 2. 70 g = 92. 59259259 mL = 93 mL 250 mL of Al x 2. 70 g / 1 mL = 675 g = 680 g 2 Using the density value we can indirectly obtain distances that are too small to measure directly. 4. A sample of aluminum foil has a length of 10. 0 cm and a width of 5. 7 cm. If the aluminum foil weighs 0. 234 g, what is the thickness of the aluminum foil?Remember that the density of aluminum is 2. 70 g/mL. (6 pts) Volume of Al = length x width x thickness = mass / density 0. 234 g x 1 mL / 2. 70 g = 0. 0866666666 mL 0. 086666666 mL / 10. 0 cm x 5. 7 cm = 0. 001520467 cm = 1. 5 x 10 3 cm E. Heat and temperature are two very important concepts. 1. In your own words, please state the difference between heat and temperature. What is a common unit of each? (5 pts) Heat measures the total energy of a sample and temperature measure the intensity of heat or the average heat of a sample. A common unit of heat is a calorie and a common unit of temperature is Kelvin.It is important to be able to convert from one temperature unit to another. 2. Aluminum melts at 1220 F. (You can see why aluminum is not a liquid at room temperature) What is the melting point of aluminum in degree Celsius ( C) and in Kelvin o C (6 pts) (K)? (oF 32 oF) x 100 oC = 180 oF (1220 oF 32)(100 / 180) = 660 oC 660 oC + 273 = 933 K o o 3. Give the ions present and their relative numb ers in potassium sulfate. a) b) c) d) e) 1K+ and 1 SO42K+ and 1 SO321K+ and 2 SO422K+ and 1 SO423K+ and 1 SO43- 3 4. How many cm2 are in an area of 4. 21in2? a. b. c. d. e. 10. 7 cm2 114 cm2 27. cm2 1. 66 cm2 1. 14 cm2 5. In performing a multistep calculation, when should you round off the answer in the calculator display? (5 pts) In a multistep calculation you should round off the answer at the end of the calculation E. Matter and Energy. 1. We learned four terms in chapter 4, heterogeneous mixture, homogeneous mixture, compound, and element. Please an example of each. (8 pts) An example of a heterogeneous mixture is the earths crust. A heterogeneous mixture can be separated into pure substances by physical methods. An example of a homogeneous mixture is salt water.The properties of a homogeneous mixture constant for a given sample. An example of a compound is NaCl. A compound can be broken down into elements by ordinary chemical reactions. An example of an element is Na. An elemen t is a substance that can not be broken down further by a chemical reaction. 2. Match Symbols and Names (10 pts) 1. sodium 2. iron 3. carbon 4. nitrogen 5. phosphorous d c e b a a. P b. N c. Fe d. Na e. C 4 1. Cl 2. Ce 3. Cu 4. Co 5. Ca e c b d a a. Calcium b. Copper c. Cesium d. Cobalt e. Chlorine 3. Give an example for each of the following terms (8 pts) a. hysical property Appearance, melting point, boiling point, density, heat and electrical conductivity, solubility, and physical state under normal conditions are all examples of physical properties. b. chemical property A chemical property of a substance describes its chemical reactions with other substances. The chemical property of sodium states that sodium will react with water to form hydrogen gas. c. physical change A physical change include changing shape, volume, or physical state. For example when water changes to ice. d. chemical change A chemical change always involves the formation of a new substance.Gas bubbles f rom the reaction of calcium with water. Fill in the blanks of the following table Symbol number of protons number of neutrons number of electrons mass number 37 Cl17 20 18 48 Cr3+ 24 24 21 24 Mg 12 12 12 37 48 24 Might not be on test. Ask teacher. Chlorine has two stable isotopes with masses of 34. 97 amu and 36. 97 amu. What is the relative abundance of the two isotopes? a. b. c. d. e. 50. 00% 35Cl and 50. 00 % 37Cl 35. 45% 35Cl and 64. 55 % 37Cl 64. 55% 35Cl and 35. 45% 37Cl 24. 23% 35Cl and 75. 77 % 37Cl 75. 77 % 35Cl and 24. 23 % 37Cl 5

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