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T1-191919elab

T1-191919elab - Test 1 Feb 5 2010 CH 101Code 191919 Name...

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Test 1 Feb 5, 2010 CH 101Code 191919 Name:________________ Grade distribution after the curve: 0 5 10 15 20 25 30 35 40 0 10 20 30 40 50 60 70 80 90 100 110 More F req u en c y Bin Histogram Frequency OK Here is the annotated version of the test of the 191919 version. The answers for 282828 were a little scrambled, (say A instead of B as the correct answer), apart for one or two items that were really different. As I discarded the last questions because of the printing problem I will only give the answers for the 14 questions I used for the grading. The grade points are based on the final calculation (including curve) which is why they add up to 140 points in total. Question 1 When a string of a harp is plucked in the middle, the string will mostly vibrate in its lowest harmonic. The only parts of the string that do not move are the points where it is attached to the instrument. The speed of sound c sound is much lower than that of light. At room temperature it is only about 343 [m/s] in the Earth’s atmosphere. Neglecting the influence of the tension of the string and its

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mass, calculate the length of a string that produces a tone of a standard A (Its frequency is 440 Hz or 440 s -1 ). The length is approximately: A. 78 cm B. 39 cm C. 150,920 m D. 1.28 m E. 2.56 m Using the formula λν =c that I wrote on the board you can calculate the wavelength λ = 343 [m/s] / 440 [1/s] = 78 cm. If you had that as an answer you had 8 points. The correct answer is actually 39 cm, because the length of the string that has nodes at the attachment is only λ /2 (This gave 10 points) Question 2 Are the following statements true or false? 1. The Aufbau principle is a consequence of the Pauli Exclusion Principle and the fact that the number of electron of an atom increases with atomic number. TRUE 2. According to Hund two electrons tend to have the same spin when a different orbital with the same energy is available. TRUE 3. A photon in the blue part of the electromagnetic spectrum has more energy than in the ultraviolet part. FALSE A. 1= T, 2=T, 3=T B. 1= T, 2=T, 3=F C. 1= F, 2=F, 3=T D. 1= T, 2=F, 3=F
E. 1= F, 2=T, 3=F B scored 10 points, A,D and E each 4 points. Question 3 Consider the electron (EC) and valence electron (VEC) configurations of isolated atoms of K, Zn and Cl in their ground state. Select the correct statement A. EC(K) = [Ar]3s 1 VEC(Zn)=3s 2 VEC(Cl)=2s 2 2p 5 B. EC(K) = [Ar]5s 1 EC(Zn)=3s 2 3d 10 EC(Cl)=[Ne]2s 2 2p 5 C. VEC(K) = 4s 1 VEC(Zn)=4s 2 3d 10 VEC(Cl)=2s 2 2p 5 D. EC(K) = [Kr]3s 1 EC(Zn)=4s 2 EC(Cl)=3s 2 3p 5 E. None of the above The correct answer is E: none of the above, because the correct configurations are: VEC(K) = 4s 1 VEC(Zn)=4s 2 3d 10 VEC(Cl)=2s 2 2p 5 E gave 10 points, C scored 6 points Question 4 Consider the hypothetical atoms A, B and C, of which the energy diagram is shown above.

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T1-191919elab - Test 1 Feb 5 2010 CH 101Code 191919 Name...

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