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In water conservation, chemists spread a thin film of a certain inert material over the surface of water to cut down on the rate of evaporation of water in reservoirs. This technique was pioneered by Benjamin Franklin three centuries ago. Franklin found that 0.10 mL of oil could spread over the surface of water about
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- Potassium sulfate has a solubility of 15 g/ 100 g water at 40C. A solution is prepared by adding 39.0 g of potassium sulfate to 225 g of water, carefully heating the solution, and cooling it to 40C. A homogeneous solution is obtained. Is this solution saturated, unsaturated, or supersaturated? The beaker is shaken, and precipitation occurs. How many grams of potassium sulfate would you expect to crystallize out?arrow_forward1.87 A solution of ethanol in water has a volume of 54.2 mL and a mass of 49.6 g. what information would you need to look up and how would you determine the percentage of ethanol in this solution?arrow_forwardYou can analyze for a copper compound in water using an instrument called a spectrophotometer. [A spectrophotometer is a scientific instrument that measures the amount of light (of a given wavelength) that is absorbed by the solution] The amount of light absorbed at a given wavelength of light (A) depends directly on the mass of compound per liter of solution. To calibrate the spectrophotometer, you collect the following data: Plot the absorbance (A) against the mass of copper compound per liter (g/L), and find the slope (m) and intercept (b) (assuming that A is y and the amount in solution is x in the equation for a straight line, y = mx + b). What is the mass of copper compound in the solution in g/L and mg/mL when the absorbance is 0.635?arrow_forward
- As part of a science project, you study traffic patterns in your city at an intersection in the middle of downtown. You set up a device that counts the ears passing through this intersection for a 24-hr period during a weekday. The graph of hourly traffic looks like this. a. At what time(s) does the highest number of cars pass through die intersection? b. At what time(s) does the lowest number of cars pass through die intersection? c. Briefly describe the trend in numbers of cars over the course of die day. d. Provide a hypothesis explaining the trend in numbers of cars over the course of the day. e. Provide a possible experiment that could test your hypothesis.arrow_forwardThe label on a bale of mulch indicates a volume of 1.45 ft3. The label also states that the mulch in the bale will cover an area of a garden 6 ft 6 ft to a depth of 1 in. Account for the discrepancy in the given volumes.arrow_forwardAlthough the preferred SI unit of area is the square meter, land is often measured in the metric system in hectares (ha). One hectare is equal to 10,000 m2. In the English system, land is often measured in acres (1 acre = 160 rod2). Use the exact conversions and those given in Exercise 47 to calculate the following. a. 1 ha = __________ km2 b. The area of a 5.5-acre plot of land in hectares, square meters, and square kilometers c. A lot with dimensions 120 ft by 75 ft is to be sold for 6500. What is the price per acre? What is the price per hectare?arrow_forward
- Gold leaf, which is used for many decorative purposes, is made by hammering pure gold into very thin sheets. Assuming that a sheet of gold leaf is 1.27 105 cm thick, how many square feet of gold leaf could be obtained from 28.35 g gold? The density of gold is 19.3 g/cm3.arrow_forwardOn October 21, 1982, the Bureau of the Mint changed the composition of pennies (see Exercise 120). Instead of an alloy of 95% Cu and 5% Zn by mass, a core of 99.2% Zn and 0.8% Cu with a thin shell of copper was adopted. The overall composition of the new penny was 97.6% Zn and 2.4% Cu by mass. Does this account for the difference in mass among die pennies in Exercise 120? Assume the volume of the individual metals that make up each penny can be added together to give the overall volume of the penny, and assume each penny is the same size. (Density of Cu = 8.96 g/cm3; density of Zn = 7.14 g/cm3).arrow_forwardHexane (C6H14, density = 0.766 g/cm3), perfluoro-hexane (C6F14, density = 1.669 g/cm3), and water are immiscible liquids; that is, they do not dissolve in one another. You place 10 mL of each in a graduated cylinder, along with pieces of high-density polyethylene (HDPE, density = 0.97 g/cm3), polyvinyl chloride(PVC, density = 1.36 g/cm3), and Teflon (density = 2.3 g/cm3). None of these common plastics dissolves in these liquids. Describe what you expect to see.arrow_forward
- Some scientists think there are living things smaller than bacteria (New York Times, January 18, 2000, p. D1). Called nanobes, they are roughly cylindrical and range from 20 to 150 nm long and about 10 nm in diameter. One approach to determining whether nanobes are living is to estimate how many atoms and molecules could make up a nanobe. If the number is too small, then there would not be enough DNA, protein, and other biological molecules to carry out life processes. To test this method, estimate an upper limit for the number of atoms that could be in a nanobe. (Use a small atom, such as hydrogen.) Also estimate how many protein molecules could fit inside a nanobe. Do your estimates rule out the possibility that a nanobe could be living? Explain why or why not.arrow_forwardA sample of 14.2 cm3 of aluminum, in powdered form, was mixed with an excess of iron(III)oxide. A reaction between them was initiated that formed aluminum oxide and metallic iron. How many cubic centimeters of metallic iron were formed? (The density of aluminum is 2.70 g/cm³ and the density of iron is 7.86 g/cm³.) TI cm3arrow_forward. A sample of an ethanol-water solution has a volume of 52.5 cm³ and a mass of 49.6 g. What is the percentage of ethanol (by mass) in the solution? (Assume that there is no change in volume when the pure compounds are mixed.) The density of ethanol is 0.789 g/cm³ and that of water is 0.998 g/cm³. Percentage of ethanol = b. Alcoholic beverages are rated in proof, which is a measure of the relative amount of ethanol in the beverage. Pure ethanol is exactly 200 proof, a solution that is 50% ethanol by volume is exactly 100 proof. What is the proof of the given ethanol-water solution? proof Submit Answer % [References] Try Another Version 10 item attempts remainingarrow_forward
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