Chemistry homework section 1 PDF

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This the first set of homework problems for the 1st half of the class...

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Due April 5th

Shayla Beck

Homework #1 Particles of Matter 30) What is the mass in kilograms of a 130-pound human standing on Earth? 58.5 kg 32) Someone wants to sell you a piece of gold and says it is nearly pure. Before buying the piece, you measure its mass to be 52.3 grams and find that it displaces 4.16 mL of water. Calculate its density and consult Table 1 to assess its purity. 52.3/4.16 = 12.6, this gold is not pure, pure gold is 19.6 g/cm^3 so this is around 64% pure. 33) What volume of water would a 52.3-gram sample of pure gold displace? -The density of gold is 19.3 g/mL. V=m/d=52.3g/19.3 g/ml = 2.71mL 34) How many joules are there in a candy bar containing 230,000 calories? 962320000 Joules 36) You measure the pressure of the four tires of your car each to be 35.0 pounds per square inch (psi). You then roll your car forward so that each tire is upon a sheet of paper. You outline the surface area of contact between each tire and the paper, which you later measure to be 32.0 square inches. What is the weight of your car? 32.0x35.0 = 1120lb. Standard gravitational field 32.174 ft/s^2/ Weight of car 1120x32.174. Cars weight is 36034.88 pound force. 38) Rank the following in order of increasing volume: a) Bacterium b) Virus c) Water molecule A>B>C 39) Rank the following in order of increasing temperature: a) 100K b) 100˚ C c) 100˚ F AC 44) You take 50mL of small BB’s and combine them with 50 mL of large BB’s and you get a total of 90mL of BB’s of mixed size. Explain. Atoms and molecules are mostly space, so then when these are mixed the spaces are filled causing it to weigh less. 45) You take 50 mL of water and combine it with 50 mL of purified alcohol and you get a total of 98 mL of mixture. Explain. The 50mL plus the 50mL do not add up to 100 mL because within the mix, many of the smaller water molecules can fit within the pockets of space that were empty in the 50 mL of larger

ethanol molecules. This is analogous to the previous question involving the BB’s and is yet another example where the existence of molecules helps to explain observed phenomena. 48) What is wrong with the following depiction of a chemical reaction? One box contains more atoms than the other. 50) Can an object have mass without having weight? Can it have weight without having mass? You can have mass without weight, but you can’t have weight without mass. 52) Which weighs more: a liter of water at 20˚C or a liter of water at 80˚C? A liter of water at 20˚C because the water molecules are going to be much more densely packed. 54) What happens to the density of a gas as the gas is compressed into a smaller volume? The density of the gas increases along with the decreasing volume. 60) Consider a ball thrown straight up in the air. At what position is its kinetic energy of a pendulum bob at a maximum? At what point is its potential energy at a maximum. The kinetic energy is a maximum as soon as the ball leaves the hand. Potential energy is a maximum ball has reached its zenith. 62) Which has more total energy: a cup of boiling water at 100˚C or a swimming pool of slightly cooler water at 90˚C? The swimming pool. 64) Distinguish between temperature and heat. Temperature is the quantity that tells us how warm or cold an object is. Heat is energy that flows from a higher-temperature object to a lower-temperature object. 65) An old remedy for separating two nested drinking glasses stuck together is to run water at one temperature into the inner glass and then run water at a different temperature over the surface of the outer glass. Which water should be hot, and which should be cold? The glass will contract when cold and expand when warmed. Fill the inner glass with cold water while running hot water over the outer glass to help separate the two. 68) Which has stronger attractions among its submicroscopic particles: a solid at 25˚C or a gas at 25˚C? The attractions among the submicroscopic particles of the solid must be stronger than the attractions among the particles of gas. 69) The following leftmost diagram shows the moving particles of a gas within a rigid container. Which of the three boxes on the right (a,b, or c) best represents this material upon the addition of heat. B. the trail lines behind each circle in this diagram are meant to indicate that the particles are moving faster. In diagram A it is showing the particles congregated to one side of the box. This is an unlikely scenario because the motion of gaseous particles is randomly oriented. In diagram C it shows fatter gas particles. Upon addition of heat, gas particles don’t grow any fatter. Instead, they move faster, which is to say they have a greater average kinetic energy. 70) The following leftmost diagram shows two phases of a single substance. In the middle box, draw what these particles would look like if heat were taken away. In the box on the right, show what they would look like if heat were added. If each particle represents a water molecule, what is the temperature of the box on the left? In the middle box particles would be drawn as if heat was taken away and the particles got condensed reducing the kinetic energy in them whereas the right box they would be drawn as heat was added. If each particle represents a water molecule. The temperature of the box on the left is 0˚C as it is in liquid state. This is because at 0˚C temperature the partial water molecules are in liquid state and partial are in solid state as seen.

74) At a depth of about 10 meters the water pressure on you is equal to the pressure of 1 atmosphere. The total pressure on you is therefore 2 atmospheres—1 atm from the water and 1 atm from the air above the water. When the following glass is pushed down to a depth of around 10 meters in depth, what will be the level of the water on the inside of the glass? The air inside the glass will experience more pressure or higher pressure when it is pushed down to the depth of around 10 meters this is according to the Boyle’s law. In the increasing pressure the volume of the gas is decreased. At 10 meters depth pressure of the gas is doubled. According to Boyle’s law volume of the gas decreased by half of water level will increase to half of the glass. Therefore the volume of the air inside the glass will decrease by half and the level of the water will rise to half mark of the glass. 75) Why do you suppose that airplane windows are smaller than bus windows? Airplane windows are small because the pressure difference between the inside and outside surface results in large net forces that are directly proportional to the window’s surface area. Larger windows would have to be proportionately thicker to withstand the greater net force— windows on underwater research vessels are similarly small. 79) A child’s lost helium-filled rubber balloon rises higher and higher into the sky. What eventually happens to the balloon? What happens to the helium? The rubber balloon will expand until it eventually pops. The material of the balloon will fall back to the Earth, and the helium will continue on its way to outer space. 80) Use Boyle’s Law to explain why a package of chips puffs up on a board a high-flying airplane. Less pressure is pushing on the bag from the outside, due to the less atmospheric pressure. 81) An airliner cruises around 30,000 feet, but the cabin is kept at more comfortable pressure that corresponds to around 8000 feet, which is about 0.743 atmospheres. For most people, the cabin would be even more comfortable if it were kept at a pressure of 1.00 atmospheres. Why don’t airlines pressurize their cabins to 1.00 atmospheres? Which gas law applies? To increase the pressure within the cabin of the airplane from 0.743 atm to 1.00 atm would require adding more air molecules to the cabin. This is an application of Avogadro’s Law. These added air molecules have weight, which makes the plan heavier. As any pilot knows, the heavier the plane, the more fuel that must be consumed to fly at a given speed. The choice, therefore, is to increase the cabin pressure and speed up. A cabin pressure corresponding to around 8000 feet is the happy medium, although it does explain, in part, why flying can be a stress to the body. Homework #2 Elements of Chemistry 21) What are the two main approaches to building nanoscale materials and devices? The top-down approach in which nanostructures are carved out of a larger materials and the bottom-up approach in which nanostructures are pieced together atom by atom. 32) Rank the following compounds in order of an increasing number of atoms: a) C12H22O12- 46 b) Buckminsterfullerene, C60-60 c) Pb(C2H3O2)2-15 B>A>C 33) Rank the following in order of increasing purity: a) Mountain spring water

b) Distilled water c) Ocean water C-A-B 35) A cotton ball is dipped in alcohol and wiped across a table top. Explain what happens to the alcohol molecules deposited on the table top. Is this a physical or chemical change? The molecules of the alcohol evaporate into the gaseous phase, which is a physical change. 38) Each night you measure your height just before going to bed. When you arise each morning, you measure your height again and consistently find that you are 1 inch taller than you were the night before but only as tall as you were 24 hours ago! Is what happens to your body in this instance best described as a physical change or a chemical change? Physical change because it readily reverses. 39) Classify the following changes as physical or chemical. a) Grape juice turns to wine- Chemical b) wood burns to ashes- Chemical c) water begins to boil- Physical d) a broken leg mends itself- Chemical e) grass grows- Chemical f) an infant gains 10 pounds- Chemical g) a rock is crushed to powder- Physical 43) Why is water not classified as an element? Water use to be classified as an element, but that was before people recognized that the basic building block of matter is these tiny particles called atoms. Today, an element is identified as a material consisting of only one kind of atom. 44) What do diamonds, buckyballs, nanotubes, and graphite have in common? Diamonds, buckyballs, nanotubes, and graphite all have carbon atoms. In each compound, carbon bonds to one another, yet they bond in different ways. The structures that compromise each compound are in a different order. 48) Name 10 elements available to you as a modern-day consumer. O,Au,Ag,Pt,Cu,Al,C,Pb,Fe,He 49) Strontium, Sr (number 38) is especially dangerous to humans because it tends to accumulate in calcium-dependent bone marrow tissues (calcium, Ca, number 20). How does this fact relate to what you know about the organization of the periodic table? Calcium is readily absorbed by the body for the building of bones. Because calcium and strontium are in the same atomic group, they have similar physical and chemical properties. The body, therefore, has a hard time distinguishing between the two, and strontium is absorbed as though it were calcium. 52) A sample of iron weighs more after it rusts. Why? Because the iron bonds with oxygen, so the weight becomes the original weight of iron plus the original weight of Oxygen. 59) What is the name of the compound with the formula Sr3(PO4)2? Strontium phosphate. Not that with polyatomic ion, the convention is to leave out the tri- or disuffixes. So to a chemist, the name tristrontium diphosphate would sound a little weird and overdone, but he or she would know what you meant.

60) Give the name and formula for a compound resulting from the combination of aluminum, sulfur, and oxygen. Aluminum sulfate Al2S3O12. 61) Elemental copper, Cu, is copper color. Elemental sulfur, S8, is yellow. What does this tell you about the color of the compound copper sulfide, CuS? Nothing. The properties of a compound are uniquely different from the properties of the elements use to make that compound. Copper sulfide, CuS, reveals itself as a dark black powder. 62) Oxygen, O2, has a boiling point of 90K (-183˚C), and nitrogen, N2, has a boiling point of 77K (196˚C). Which is a liquid and which is a gas at 80 K (-193˚C) The oxygen is a liquid at 80K while the nitrogen is a gas at this temperature. This is because 80 K is a higher temperature than the 77K boiling point of nitrogen but a lower temperature than the 90 K boiling point of oxygen 65) How might you separate a mixture of sand and salt? How about a mixture of sand and iron? Add the mixture of sand and salt to some water. Stir and then filter sand. Rinse the sand several times with fresh water to make sure all of the salt has been removed. Collect all the salty water and evaporate the water. The residue that remains will be the salt. After the sand dries, you’ve got just the sand. For a mixture of sand and iron, take advantage of the fact that only iron is attracted to a magnet. 68) Which of the following boxes shown best represents a suspension? A solution? A compound? A suspension, solution, and a compound are identified in boxes A,B, and C. In box A, a compound is identified due to an even distribution of elements. In box B, a solution is present since there is only one identifiable substance. Box C represents a suspension because there is a clear separation between molecules. 69) Classify the following as a(an) homogeneous mixture, heterogeneous mixture, element, or compound: table salt, blood, steel, planet Earth. Table salt is generally a heterogeneous mixture of the compound sodium chloride and desiccants that absorb moisture, preventing the salt from clumping. Blood is a suspension, which is an example of a homogeneous mixture. Steel is a solid solution, which is a homogeneous mixture, consisting of mostly iron and smaller amounts of carbon and nickel. Planet Earth is a heterogeneous mixture. 70) Classify the following element, compound, or mixture, and justify your classifications: salt stainless steel, tap water, sugar, vanilla extract, butter, maple syrup, aluminum, ice, milk, cherry-flavored cough drops. Salt- Compound Stainless steel- Mixture Tap water- compound Sugar- compound Vanilla extract- mixture Butter- mixture Maple syrup- mixture Aluminum- element Ice- compound Milk- mixture Chery flavored cough drops- mixture

Homework #3 Subatomic Particles 36) Rank the three subatomic particles in order of increasing mass: a) The neutron b) The proton c) The electron C>B>A 37) Consider these atoms: helium, He; chlorine, Cl; and argon, Ar. Rank these in terms of their atomic number, from smallest to largest Helium, Chlorine, Argon 40) Consider these atoms: helium, He; aluminum, Al; and argon, Ar. Rank them, from smallest to largest: (a) in order of size and (b) in order of the number of protons. A) helium, argon, aluminum B) Argon, aluminum, helium 41) Consider these atoms: potassium, K; sodium, Na; and lithium, Li. Rank them in order of the ease with which they lose a single electron, from easiest to most difficult. Potassium, Sodium, Lithium. 42) Rank these atoms in order of the number of electrons they tend to lose from fewest to most: sodium, Na; magnesium, Mg; and aluminum, Al. Na...