Solutions to Chapter 2 Homework: Atomic Structure and Chemical Formulas, Assignments of Chemistry

Download Solutions to Chapter 2 Homework: Atomic Structure and Chemical Formulas and more Assignments Chemistry in PDF only on Docsity! Chapter 2 Homework: solutions 14. a) The charge of a droplet is due to one or more extra electron(s) residing on the droplet. Thus different charges correspond to different number of extra electrons. b) We can see that all the charges are roughly multiples of 1.6*10-19 C; it is reasonable to assume that is a charge of a single electron. Then droplets A, B, C, and D have 1, 2, 3, and 4 excess electrons. c) If assumption in part b) is correct, then the electronic charge for droplets A-D is (in 10-19 C): 1.60, 1.58, 1.60, and 1.58 (all to 3 significant figures). The average value will then be 1.59*10-19 C (3 significant figures). 24. Since these are all neutral atoms, number of protons = number of electrons. Mass number = number of protons + number of neutrons. Number of protons determines the identity of the element; the mass number determines the isotope. 28. a) By definition it is 12 amu. b) The atomic weight of carbon is reported as 12.011 amu, because carbon found in the nature is a mixture of three isotopes: 12C (most common), 13C, and 14C. 12.011amu is the average mass of a carbon atom (as found in the nature). 29. Average atomic mass= 69.17% of 62.9296 amu + 30.83% of 64.9278 amu AW= 0.6917*62.9296 amu + 0.3083*64.9278 amu = 63.55 amu Note: each percentage has only 4 sigfigs => the terms to sum will be significant only to 2 decimal places and so will be the sum. 36. a) sodium; metal b) titanium; metal c) gallium; metal d) uranium; metal e) palladium; metal f) selenium; nonmetal g) krypton; nonmetal 37. a) K; alkali metals (1A); metal b) I; halogens (7A); nonmetal c) Mg; alkaline earth metals (2A); metal d) Ar; rare gases (8A); nonmetal e) S; chalcogens (6A); nonmetal 40. The compounds with the same empirical formula may have different molecular formula, i.e. these may be molecules of very different size and properties. For example, compounds with empirical formula CH2 include, among others, ethylene (C2H4; gas), cyclohexane (C6H12; liquid), and 1-eicosene (C20H40; solid). Symbol 121Sb 103Rh 88Sr 127Te 239Pu Protons 51 45 38 52 94 Neutrons 70 58 50 75 145 Electrons 51 45 38 52 94 Mass number 121 103 88 127 239 42. a) benzene: molecular formula C6H6; empirical formula CH b) silicon tetrachloride: molecular and empirical formula SiCl4 c) diborane: molecular formula B2H6; empirical formula BH3 d) glucose: molecular formula C6H12O6; empirical formula CH2O 43. a) 6 (5+1) b) 6 (3 hydrogen atoms in each acetate ion => 3*2) c) 12 (4 hydrogen atoms in each ammonium ion => 4*3) 48. 49. a) 2+ b) 3+ c) 1+ d) 2- e) 1- 51. a) GaF3; gallium fluoride (gallium is in group 3A, it is going to behave like aluminum) b) LiH; lithium hydride (H is above Li, so Li goes first) c) Al3I; aluminum iodide d) K2S; potassium sulfide 54. a) Cu2S b) Fe2O3 c) Hg2CO3 d) Ca3(AsO4)2 e) (NH4)2CO3 55. a) molecular b) molecular c) ionic d) ionic e) ionic f) molecular g)molecular h) ionic 57. a) ClO2- b) Cl- c) ClO3- d) ClO4- e) ClO- 58. a) selenate (analogue of sulfate, SO42-) b) selenide (analogue of sulfide, S2-) c) hydrogen selenide (analogue of hydrogen sulfide, HS-) d) hydrogen selenite (analogue of hydrogen sulfite, HSO3-) 59. a) magnesium oxide b) aluminum chloride c) lithium phosphate d) barium perchlorate e) copper(II) nitrate (or cupric nitrate) f) iron(II) hydroxide (or ferrous hydroxide) g) calcium acetate h) chromium(III) carbonate (or chromic carbonate) i) potassium chromate j) ammonium sulfate Symbol 75As3- 59Ni2+ 127I- 197Au3+ Protons 33 28 53 79 Neutrons 42 31 74 118 Electrons 36 26 54 76 Net charge 3- 2+ 1- 3+