CHEM 20A Fall - 2005 Midterm 1

CHEM 20A Fall - 2005 Midterm 1 - Chemis 20A-1 version A D...

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Unformatted text preview: Chemis 20A-1 version A D .E.R Scerri 'd Term 1, O tober 2005 Name _ _ v Last, First Signature_' I 5 ID# - 5“. V4“ TA name_ Instructions: This exam has 4 q stions plus a periodic table at end of exam. Verify you have the righ number of pages before you begin. Write your name on each page. Raise your hand if you don't understand a ' ! No credit will be given for an For uestions re uirin lanations do not exceed the line limit shown b dott (1 lines. If on do it will not even be read b the ra er! Possibly useful information: 12 inches = 1 foot, 2.54 cm = 1 inch. h = 6.63 x 10-34 J sec N0 = 6.02 x 1023 mol-1 0 = 3.00 x 108 m sec-1 me = 9.11 x 1&31 kg 1a.m.ui = 1.66 x 10-27 kg 1A = 10-10111 g = 9.81 m/s 1 eV = 1.602 1410'ng Velemmcm cc Q1Q2/r; K.E. =1/2mv2 = p2/2m F = -AV/Ar 7W = 0 AB = Ef' E1 = sphomn = hv hv = hv0 + K. E.(e1ectron) = *3; =% mAvAx = Apr Z Eh; En : -(2.18 x 10'18 J)zefi2/n2; rn= (0.529 Ayn/2mgf n—1~—1 spherical (radial) nodes; 1 angular nodes; n-1 total nodes 71/ ,4 . ‘ I my 7" Sketch a diagram of the lefi-step periodic table and label the various blocks as s, What is the most controversial a5pect of this form of the periodic table? Explain ._;i - . 2’ ' -\ ' -t ‘ U s =. ,1- “’sz [1’ "f,/ i ’ 2/. -‘ “Cf.--JE’§£L.-:§§;:£L-Z_-L_L;a;4-vyina---___;_:._____--___---_---- ’_-42.;42;;__;_---;£.;-_;;;L.i-;--;;44:42.";;it--;.:;é:_igéfi_4%&é%z_carfl%ffl r la. p, d and f. t Vii—a. 1b. briefly. 10. Why are the lanthanides and actinides (rare earth elements) usually shown as a footnote to the main] periodic table? 1d. Sketch an alternative periodic ble that incorporates these elements into the main body of the periodic table. Indi ate the position of the rare earth elements as a whole. IF” r, p . (3) .:i::f’ @ l a l v i J J I -— 7..-.5 drawn-m?“ v.._+ . ‘- le. Explain the relationship(s) between the elements in a "triad" and give an example. 4 2.a 2b. 2c. 2d. How does Rutherford's model (electrons orbiting randomly) explain the occurrence of atomic spectra. ------------------------------------ -q Thomson's plumb pudding mojel gave way to Rutherford's model of the atom. What was the experime tal evidence for this change? (3) "f;._z£i£__{flz_é_‘:i2;.€z.fl;“arraififf .1 {.2/ I '(rlg’; 7‘. r; “A! - " ' V, _/ (.4! > Ida-n.4, ‘ 13.1,. 5.; I I - - r -;.’./‘£4r.;.iu__‘__g__-L-AL(I4’:—Ifl;fl-fi---_i-__: .... ..‘._-...._’_---..A'.. ....... --,.'i . . . . . .... Calculate the quantum mechanical wavelength of an object weighing 3.52 x 10'20 (3) grams travelling at a velocity of 160. mfsec. A‘EHL. _ I‘__ ’ ( _. L 3,, rm“ What are the necessary conditions needed to obtain diffraction and interference effects from any form of radiation? Your response should mention the path lengths of waves as well as the dimensions of slits or obstacles. (4) .,4»2_c_/z_rz_:a;zi_£§:-.ri£:_-mi-.{f__;:;£;._i_:Le.---1413: ___________ ’X /\ 3a. 3b. 3c. An atom of a rare earth element is illuminated at a wavelength of 8612 Angstroms. The surface of the inetal emits a photoelectron with a kinetic energy of 1.07r x 10%.}. Calculate the Work function for this metal. I 3. am: 2; (5) —- .. 0:37 ’0'”? Calculate the energy (with the correct Sign) and frequency of a spectral line associated with the transition from n = 6 to n = 4 in a Be+3 ion. a" : ,/ f6 x 4/,- “ 4/ -_ .1; [~ 23V 1/" w)'Z/Xf0fz. MI 3 i 2 (5) :1} x, H How does Schrodinger's approach improve on Bohr's explanation of quantization? (4) __ f I, i. ,‘ ' ' , ‘ I. $52.5 ........ __:"___'____fL _______________________________________________ .— Ammonia can be manufactured (a) Balance the equation below. IN2 + by reacting nitrogen with hydrogen. in —> 'Z_NH3 (b) From this balanced equation determine the limiting reagent when 260 kg of nitrogen are reacted with 12.0 kg of hydrogen. 2/ K) 2‘9 1.1.7105 rr'hdfflj? «Q P “.7? r? y‘r'tlrlj‘ : (c) If the process occurs with a 90% yield how many kilos of ammonia should be obtained? ’2 7% Vqfl I) fly ‘ If (1/ igthfl‘f ’ ‘i/ ‘ ’ z “7" 1' N r / » :WM FEW»: (31,6! AWL?) : (3) (d) Calculate the atomic mass of element X which has three isotopes with amu, and 23.20 amu. The relative abundances are masses 20.04 amu, 21.02 29%, 40% and 31% respectively. '1 .' ,1 _. ‘ Page , 5+ “I (3) v. ...
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This test prep was uploaded on 02/20/2008 for the course CHEM 20A taught by Professor Scerri during the Fall '05 term at UCLA.

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CHEM 20A Fall - 2005 Midterm 1 - Chemis 20A-1 version A D...

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