# J Gibbs Chapter 8 Post Lecture Assignment

**Unformatted text preview: **Part A How many peaks will be present in a mass spectrum for BrCl? Express your answer as an Integer. Hint 1. How to approach the problem A mass spectrum shows the relative number of molecules in the sample plotted against molecular mass. In other words, there is a peak in the spectrum for each unique mass corresponding to a different molecule in the sample. Although the sample contains only BrCl molecules, not every molecule has the same mass because of the different isotopes of bromine and chlorine present. Think about how many combinations of bromine and chlorine can be made using the isotopes 35 Cl, 37Cl, 79Br, and 81Br. The number of combinations is directly related to the number of peaks present in the mass spectrum. Also note that a mass spectrum is sensitive enough to distinguish masses that differ only in the sixth significant figure. ANSWER: [�-� Co1T8ct The four different molecules are • s1Br37Cl, • 81Br35CI, • 79Br3 7 Cl, and • 79Br36Cl. Part B What are the masses of the four different BrCl molecules? Express the masses in atomic mass units using six significant figures, in dac:reasing numeric order (highest to lowest}, uparatad by commas. Hint 1. Calculate the mass of 79 Br35 Cl The mass of a molecule is the sum of the masses of its constituent atoms. Given the masses shown here, Atom Mass (amu) 79Br 78.918 asc1 34.969 calculate the mass of a 79Br36 Cl molecule. Express the mass in atomic mass units using six significant figuraa. ANSWER: I , ,,•..., amu ANSWER: 117.882, 115.885, 115.884, 113.887 amu ...

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**Unformatted text preview: **What is the weight, in pounds, of a 255-kg object on Jupiter? Express the weight numerically in pound•. Hint 1. How to approach the problem You must convert the mass to a \Wight before applying the relative force of gravity on Jupiter. One way to convert this mass, m, to a weight, W, is to first convert m to pounds, then apply the formula W = m · g, where g = 1.00 lb/lb. Finally, factor in the relative force of gravity on Jupiter. Hint 2. Convert the mass of the object to pounds Convert a mass of 255 kg to pounds. Recall that 1 lb= 0.454 kg. Express the mass numertcally In pounds. ANSWER: [ m= 562 lb ANSWER: W= 1330 lb Correct T he following conversion of the constant g shows how 9.81 N/kg is equal to 1 lb/lb: t w = g.Sl N ( eigh ) X I lb (weight) X 0.454kg (mass) = l.OO lb (weight) lb (mass) kg (mass) 4.45 N (weight) l lb (mass) Note that pounds can be a unit of weight or mass. g Learning Goal: To analyze the experiment used to determine the properties of an electron. In 1909, Robert Millikan performed an experiment involving tiny, charged drops of oil. The drops were charged because they had picked up extra electrons. Millikan was able to measure the charge on each drop in coulombs. Here is an example of what his data may have looked like. Drop Charge (C) A 3.20 x 10-19 4.80 x 10-19 B c D 8.00 x 10-19 9.60 x 10-19 Part A Why did different drops have different charges? Hint 1. How to approach the problem Atoms do not cany a charge unless they have gained or lost electrons. So the number of atoms, and thus the size of the drop, does not necessarily correspond to the amount of charge carried by the drop. ANSWER: Because the drops were different sizes. Because some drops contained more atoms than others. • Because some drops had picked up more electrons than others. Co11'8ct A drop that had picked up more electrons would have a greeter charge. A drop with fewer extra electrons would have a lesser charge. Part B Based on the given data, how many extra electrons did drop C contain? Express your answer as an Integer. Hint 1. Determine the smallest increment of charge Look at the differences in charge between the drops. Drop A B c D Charge (C) 3.20 x 10-19 4.80 x 10-19 8.00 x 10-19 9.60 x 10-19 What is the smallest difference in charge between two drops? Express your answer numerically in coulombs. ANSWER: 1.eox10-19 C Hint 2. Determine the charge on a drop with four extra electrons If the charge on one electron is 1.6 x 10-19 C, what is the total charge on a drop with four extra electrons? Express your answer numerlcally In coulombs. ANSWER: [ 6.40)(10-19 c ANSWER: [� I electrons [ Correct Partc In Millikan's experiment, the charge on each drop of oil was measured in coulombs. Imagine the same experiment, but with charges measured in a fictitious unit called a zeet (Z). Drop Charge (Z) A 2.sax10-14 B 4.80x10-14 c 5.28x10-14 D 5.76x10-14 E 7.68x10-14 ...

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