Chemistry

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Question 1
Electromagnetic radiation behaves both as particles (called photons) and as waves. Wavelength () and frequency () are related according to the equation

where  is the speed of light (). The energy ( in joules) contained in one quantum of electromagnetic radiation is described by the equation

where  is Planck's constant (). Note that frequency has units of inverse seconds (), which are more commonly expressed as hertz (). Part A
A microwave oven operates at 2.40 . What is the wavelength of the radiation produced by this appliance? Express the wavelength numerically in nanometers.
   = | |     |
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Part B
Two of the types of infrared light, IR-B and IR-A, are both components of sunlight. Their wavelengths range from 1400 to 3000  for IR-B and from 700 to 1400  for IR-A. Compare the energy of microwaves, IR-B, and IR-A. Rank from greatest to least energy per photon. To rank items as equivalent, overlap them. |

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Question 2
Consider two different compounds of carbon and oxygen: carbon dioxide, , and carbon monoxide, . The number of oxygen atoms per carbon atom in  is double the number of oxygen atoms per carbon atom in . So we can predict that the mass of oxygen per gram of carbon in  is double the mass of oxygen per gram of carbon in . And, in fact, if other carbon-oxygen compounds existed, we could predict small, whole-number ratios for the masses of oxygen per gram of carbon in all of them. This is exactly what John Dalton predicted for compounds using his atomic theory of matter. It came to be known as the law of multiple proportions. Part A

There are two different compounds of sulfur and fluorine.
* In , the mass of fluorine per gram of sulfur is 3.55 . * In the other compound, , the mass of fluorine per gram of sulfur is 1.18 . What is the value of  for the second compound?
Express your answer as an integer.
  3.0
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Before the mole
The law of multiple proportions predates the concept of a mole or molar mass. Thus, scientists like John Dalton could only determine the relative amounts of each type of atom in a formula, and not the exact formula. For example, Dalton could determine that there were two carbon-oxygen compounds, one with twice as much oxygen as the other. However, he did not know for sure that the formulas were  and . Other possibilities (given what they knew at the time) could have been  and , or  and , etc. Part B

Samples of three different compounds were analyzed and the masses of each element were determined. Compound| Mass  
()| Mass  
()|
A| 5.6| 3.2|
B| 3.5| 8.0|
C| 1.4| 4.0|
If you were John Dalton and had never heard of a mole, which of the following would you think were possible sets of formulas for the compounds A, B, and C, respectively? Check all that apply.
| , , |
| , , |
| , , |
| , , |
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Question 3
Ethyl butyrate, , is an artificial fruit flavor commonly used in the food industry for such flavors as orange and pineapple. Its fragrance and taste are often associated with fresh orange juice, and thus it is most commonly used as orange flavoring. It can be produced by the reaction of butanoic acid with ethanol in the presence of an acid catalyst ():

Part A
Given 8.45 of butanoic acid and excess ethanol, how many grams of ethyl butyrate would be synthesized, assuming a complete 100 yield? Express your answer in grams to three significant figures.
 mass of ethyl butyrate = | |     |
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Part B
A chemist ran the reaction and obtained 5.30  of ethyl butyrate. What was the percent yield? Express your answer as a percent to three significant figures.  percent yield = | |     |
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