Chem HW
15.
a) Mass is conserved because Dalton’s theory says that atoms can’t be destroyed or created by chemical reactions, therefore it is conserved.
b) The composition of a substance depends on the number and type of atoms that make it up.
c) Compounds using the same elements differ by the numbers of each type of atom composing the element.
17. The cathode ray was produced from the negative electrode and repelled by the negative pole. Because the negative pole deflected the rays, and negative forces repel other negative forces, the rays were discovered to be negatively charged.
19. Atomic number is the number of protons in the nucleus of an atom of the element, while mass number is the total number of protons and neutrons in that atom. The atomic mass is the mass of the entire atom.
21. The compound,water, always contains exactly the same proportion of hydrogen and oxygen by mass. Since water contains the same proportion of elements by mass thecomposition of water does not depend on the amount of oxygen it contains.
23. (a) In a given coumpound the same relative masses of elements were always found even when there are different relative amounts of the elements.
(b) 2 volumes of HCl is formed
25. The two elements, flourine(F) and sulfur (S), formed a series of compounds. The ratios of the masses of flourine that combine with1 gram of sulfur can always be reduced to small whole numbers.
27. First, changed the hydrogen gram value to 1.00. Took table value of oxygen (1.00 g) divided it by table value of hydrogen (.126 g) to find the value to multiply the hydrogen by to make it equal 1.00 g. The value was 7.94, which I multiplied both the oxygen and hydrogen values by in order to keep them equivalent. The oxygen value became 7.94 g and the hydrogen 1.00 g. Since the assumed formula said there was 1 hydrogen per 1 oxygen and the hydrogen is at its atomic mass, the atomic mass of oxygen had to be 7.94 g. To find the atomic masses of Sodium and Magnesium, just multiply the table value in grams by the atomic mass of oxygen. You can do this because in each of the formulas, oxygen has a ratio of one to one with the other element and because they are each combining with exactly 1.00 grams of oxygen. This means that whatever you multiply the 1.00 g of oxygen by to get its atomic mass you would multiply the other element’s table values by to get their atomic masses, including hydrogen. Therefore, for sodium you multiply 2.875 by 7.94 and get its atomic mass to be 22.8 g, and for magnesium, you multiply 1.500 by 7.94 and get its atomic mass to be 11.9 g. You could do the same with hydrogen and would get 1.00 g which is the given.
-Table Atomic Masses: Oxygen=7.94g, Sodium=22.8g, Magnesium=11.9g
-Actual Atomic Masses: Oxygen=16.0g, Sodium=23.0g, Magnesium=24.3
The values found with the info from the table contradict with two of the periodic table entries. Sodium is just about the same in both results, but the oxygen and magnesium’s periodic table atomic masses are double the table’s results. The results from the table are wrong because the assumed formulas are wrong. They should be H2O, Na2O, and MgO. Oxygen came out wrong because 7.94 g was the grams of oxygen for each hydrogen. Since there is two hydrogen in water , that would be 7.94 g doubled or 15.88g, which is close to the actual atomic mass (16.0 g). Since the oxygen value was half its actual atomic mass, when I multiplied the other ones by it, they were also half the weight they should be in their actual formulas.
29. Density of Hydrogen Nucleus (D=m/v)
m=1.67e-24g
v=ðr³
v=ð(5e-13cm)³
v=ð(1e-37cm3)
v=3e-37cm3
D(nucleus)= 1.67e-24g/3e-37cm3
D(nucleus)=5.57e12g/cm3
D(nucleus)=6e12g/cm3
Density of Hydrogen Atom (D=m/v)
m=1.67e-24g
v=ðr³
v=ð(5e-8cm)³
v=ð(1e-22cm3)
v=3e-22cm3
D(atom)= 1.67e-24g/3e-22cm3
D(atom)=.00557g/cm3
D(atom)=6e-3g/cm3
31. Started out with the equation TOTAL CHARGE = Y(Whole # multiple of electron charge and the final answer) • NEGATIVE CHARGE. The TOTAL CHARGE is the given info of 5.93e-18 C. Y is the final answer, and NEGATIVE CHARGE is found through another equation (e/m = -1.76e8 C/g). Transposing that equation, you can make it into e = -1.76e8 C/g • m (e = negative charge and m = mass of electron). Plugged 9.11e-28 g into m because it is mass of an electron and solved. Got e = -1.60e-19 C. Next, transposed first equation into Y = TOTAL CHARGE/ NEGATIVE CHARGE. Plugged numbers into formula (Y = 5.93e-18 C/-1.60e-19 C) and solved. The answer was -37.0 because electron charge is negative. Therefore, the drop contains 37 negative charges.
33. Gold – Au
Silver – Ag
Mercury- Hg
Potassium- K
Iron – Fe
Antimony – Sb
Tungsten- W
35. Fluorine – F
Chlorine- Cl
Bromine- Br
Sulfur – S
Oxygen – O
Phosphorus – P
37. Sn- tin
Pt- Platinum
Co- Cobalt
Ni- Nickel
Mg- magnesium
Ba- barium
K- potassium
39. Helium, Neon, Argon, Krypton, Xenon, Radon
Radon has only radioactive elements.
41. a) 8 c) 18
b) 8 d) 5
43. a) 94, 144 d) 2, 2
b) 29, 36 e) 27, 33
c) 24, 28 f) 24, 30
45. 19/9 F
19 is over 9
47. 151/63 EU 3+
151 is over 63
3+ is a superscript
49. 34/16 S 2-
34 is over 16
2- is a superscript
51.
Symbol # of protons in nucleus # of neutrons in nucleus # of electrons Net Charge
75 As3+
33 33 42 30 3+
128 Te2-
52 52 76 54 2-
32 S
16 16 16 16 0
204 Ti+
81 81 123 80 1+
195 Pt
78 78 117 78 0
53. Metals: Mg, Ti, Au, Bi, Ge, Eu, Am
Nonmetals: Si, B, At, Rn, Br
55. a and d
57. As one goes down group 4A, the elements' atomic mass gets greater. Therefore, the metals are heavier at the bottom of the group.
59. A) Na=Lose; Na +1 B) Sr=Lose; Sr +2
C) Ba=Lose; Ba +2
D) I =Gain; I -1
E) Al=Lose; Al +3
F) S=Gain; S -2
61. A) NaCl=Sodium Chloride
B) Rb2O= Rubidium Oxide (2 should be a subscript)
C) CaS=Calcium Sulfide
D) AlI3=Aluminum Iodide (3 should be a subscript)
63. A) Chromium (VI) oxide
B) Chromium (III) oxide
C) Alminum sulfate
D) Sodium hydride
E) Calcium bromide
F) Zinc chloride
65. A) potassium perchlorate
B) calcium phosphate
C) aluminum sulfate
D) lead (II) nitrate
67. A) Nitrogen triiodibe
B) phosphorus trichloride
C) sulfur difluoride
D) dinitrogen tetrafluoride
69. A) Copper (I) iodide
B) copper(II) iodide
C) cobalt (II) iodide
D) sodium carbonate
E) sodium hydrogen carbonate or sodium bicarbonate
F) tetrasulfur tetranitride
G) sulfur hexafluoride
H) sodium hypochlorite
I)barium chromate
J) ammonium nitrate
71. A) CsBr
B) BaSO4
C) NH4Cl
D) ClO
E) SiCl4
F) ClF3
G) BeO
H) MgF2
73. A) Na2O
B) Na2O2
C) KCN
D) Cu (NO3)
E) SiCl4
F) PbS
G)PbS2
H) CuCl
I)GaAs
J) CdSe
K) ZnS
