TakeHome Exam #1Answer KeyMay 31, 2005. (Due, Thursday, June 2)
Please read:Mark the best answer among the given multiple-choices. Then, give your brief explanation next to the question somewhere.Turn in your answers before class begins on Thursday. Late exam will not be graded. Each answer worth 2 points.
1.Which of the followings are homogenous mixtures:
I) Seawater II) Gasoline III) air IV) sand V) tomato juice
A) I and IVB) I, II, and IV C) Only III D) I, II, and III E) None
2.Give the chemical symbols for the following two elements: Sodium and Copper
A) S and CB) S and CoC) Na and CD) Na and Cu E) S and Cu
- Name the following elements: C and Pb
A) Cupper and Platinum B) Cupper and Lead C) Carbon and Platinum D) Carbon and Lead
4.Which of the following is an example of the three states of matter:
A) Ice-liquid water-carbon dioxide B) Hard water-liquid water-water vapor C) Ice-liquid water-water vapor D) carbon-oxygen-carbon dioxide E) ice-milk-ice cream
5.A solid white substance “A” is heated strongly in the absence of air. It decomposes to form a new white substance “B” and a gas “C”. The gas has exactly the same properties as the product obtained when carbon is burned in an excess of oxygen. Based on these observations, can we determine whether solids “A” and “B” and the gas “C” are elements or compounds?
A) We cannot determine B) All are elements C) “A” and “B” are elements whereas “C” is compound D) “B” cannot be determined based on the data provided but “A” and “C” are compounds E) All are compounds
B could be an element or a compound, we are not sure (given information is not enough). But we’re sure that A and C are compounds.
6.Label each of the following as either a physical process (PP) of a chemical process (CP)
I) Corrosion of aluminum metal II) melting of ice III) explosion of nitroglycerin
A) All are PP B) All are CP C) I is PP but II and III are CP D) I and III are CP but II is PP E) I and II are PP but III is CP
Corrosion and explosion are chemical changes, while melting is a physical change.
7.Which of the following is not matter?
A) Dust B) light C) pizza D) elemental carbon E) none of these
8.Which one of the following is a physical change?
A) Decomposed apple B) burnt coal C) boiling water D) bread rising through the use of baking soda E) rusted iron
9.Which of the following numbers contains six significant figures?
A) 4.2010 B) 0.03702 C) 1.032 x 103 D) 1000.00 E) 493.00
10.Which is not correctly represented by the right number of significant figures?
A) (2.45/2.0) - 0.5 = 0.7 B) ((2.70/3.00) -2.0) x (1.20) = -1.32 C) 3.11 - 6.829 = -3.72 D) 2.5/2.0 = 1.3
11.Which of the statements below gives the correct relationship between units?
A) 1000 mA < 1 nA B) 100 mg > 1 g C) 10 mg < 1 dg D) 100 m < 1 cm E) 10 ks < 1000 s
12.Passing an electric current through a certain substance produces oxygen and sulfur. This substance cannot be a(n)
A) Element B) mixture C) compound D) pure substance
13. Which identification is incorrect for the elements listed?
A) S—sulfur B) C—carbon C) Cd—cadmium D) C-cupper E) Zn—zinc
- The symbol for the element potassium is
A) Po B) K C) P D) Pt E) Kr
- The high temperature during a summer day was observed to be 92°F. What was this temperature in °C?
A) 33 B) 51 C) 5/9 (92+32) = 69 D) 60 E) 28
16.For the following measured numbers, the number of significant figures is indicated in parentheses. Which is incorrect?
A) 40.04 (two) B) 2038 (four) C) 4 x 102 (one) D) 0.00142 (three) E) 0.0130 (three)
- Which set of measurements on a 2.00-gram standard is the most precise?
A) 2.10, 2.20, 2.15 B) 1.50, 2.00, 2.50 C) 2.00, 2.01, 1.98 D) 2.10, 2.00, 1.95
18. Which conversion to standard exponential notation is incorrect?
A) .324x108 = 3.24x107 B) 427x1010 = 4.27x1012 C) 0.00654x10-6 = 6.54x10-3 D) 4354x10-4= 4.354 x 10-1
19.An object will sink in a liquid if the density of the object is greater than that of the liquid. If the mass of an object is 9.83 g, what volume must it have in order for it to sink in liquid mercury (density = 13.6 g/cm3)?
A) Less than 1.38 cm3 B) less than 0.723 cm3 C) less than 7.48 cm3 D) less than 134 cm3 E) none of these
Density = mass / volume. When the volume = 9.83 g/ 13.6 g/cm3 = 0.723, the density of the object and that of mercury is the same. In order for the object to sink, it has to have larger density (or less volume than 0.723 cm3)
20.Zinc has a density of 446 lb/ft3. What is the density of zinc in g/cm3? (1 ft = 30.5 cm; 1 lb = 454 g)
A) 7.14 g/cm3 B) 3.65 g/cm3 C) 0.0323 g/cm3 D) 6.64 x 103 g/cm3
Since 1 ft = 30.5 cm, then 1 ft3 = (30.5 cm)3 hence 28372.63 cm3
21.Perform the indicated operations, expressing the answer to the proper number of significant figures. 13.236 L + 6.2 L - 5.28 L =
A) 14.156 L B) 1.756 L C) 14.2 L D) 19.436 L E) 14.16 L
Only one significant figure after decimal point (because 6.2 has least significant figure after the decimal point).
22.Naturally occurring neon (atomic number = 10) consists of two isotopes: 20Ne and 22Ne. How many neutrons are in each isotope?
A) 10 and 12 B) 12 and 10 C) 21 and 23 D) 20 and 22 E) 11 and 13
20-10 = 10 and 22-10 = 12
23.How many neutrons are there in the nucleus of a 108Ag atom (atomic number = 47)?
A) 54 B)61 C) 108 D) 47 E) none of these
24.What is the mass number of an isotope of mercury (atomic number = 80) that has 122 neutrons?
A) 202 B) 120 C) 80 D) 200 E) 122
Mass number = n + p = 122 + 80 = 202
25. Which of the following is a metal?
A) Sr B) Se C) Si D) P E) S
26. An elemental ion has 34 protons, 36 electrons, and 44 neutrons. What isotope is it?
A) B) C) D) E)
The mass number is 34 + 44 = 78, and the charge is -2 because it has two more electrons (36) than protons (34).
27. Which one of the following is incorrectly labeled?
A) Te-chalcogen B) Rn-noble gas C) Ca-alkaline earth metal D) Mg-alkali metal E) I-halogen
28. An elemental ion has 22 protons, 20 electrons, and 26 neutrons. What isotope is it?
A) B) C) D) E)
The mass number is 22 + 26 = 48, and the charge is +2 because it has twoless electrons (20) than protons (22).
29. How many protons and neutrons are there in
A) 35 protons and 80 neutrons B) 34 protons and 45 neutrons C) 80 protons and 35 neutrons D) 35 protons and 45 neutrons E) 45 protons and 35 neutrons
30. Which of the following statements is true for neutral atoms?
A) The number of neutrons in a neutral atom must always equal the number of protons.
B) The number of neutrons in a neutral atom must always equal the number of electrons.
C) It is possible for atoms of different elements to have the same number of protons.
D) It is possible for atoms of different elements to have the same number of electrons.
E) It is possible for atoms of different elements to have the same number of neutrons.
31._____ rays are a stream of fast-moving electrons.
A) Alpha B) gamma C) beta D) none of these
32. Which pair of symbols below represents isotopes?
A) H, He B) 16O, 16N C) 16O, 17O D) 13C, 14N E) Cl, Cl-
Isotopes have the same number of protons but different number of neutrons.
33. An atom containing 34 protons, 43 neutrons, and 34 electrons would have the symbol
A) 43Se B) 77Tc C) 43Tc D) 77Se E) 77Ir
34. An iron-56 nucleus contains
A) 26 protons and 26 neutrons B) 56 neutrons C) 26 protons and 30 neutrons D) 56 protons E) 56 protons and 56 neutrons
35. An element in the lower left corner of the periodic table
A) is definitely a nonmetal B) is definitely a metal C) is either a metal or metalloid D) is either a metalloid or a nonmetal E) is definitely a metalloid
36. Which one of the following should be the most similar in chemical property to strontium
A) Ba B) At C) Xe D) Rb E) Ga
37. Which one of the following is incorrectly labeled?
A) Zn-transition metal B) Cu-transition metal C) Cl-halogen D) Ga-transition metal E) Ne-noble gas
38.Which one of the following contains the greatest number of electrons?
A) P3- B) P2- C) P3+ D) P E) P2+
39.Which of the following are ionic and which are molecular? CO2; KCl; KNO3; N2O
A)KNO3 is the only ionic compound
B)B) KCl, KNO3, and N2O are the only ionic compounds
C) CO2 and N2O are the only molecular compounds
D)CO2 is the only molecular compound
E)CO2, KNO3, and N2O are the only molecular compounds
40.How many nitrogen atoms are there in CH2(NH2)2?
A) 2 B) 3 C) 6 D) 4 E) 1
41.How many carbon atoms are in CH3-O-CH2-C2H5?
A) 4 B) 1 C) 3 D) 10 E) 2
42.What is the name for CuS?
A) copper(I) sulfur B) copper sulfide C) copper(II) sulfur D) copper(I) sulfide E) copper(II) sulfide
43.Predict the product formed when calcium, Ca, combines with arsenic, As.
A) Ca3As2 B) Ca2As C) CaAs2 D) CaAs E) Ca2As3
44.Which name is incorrect?
A) CS2, carbon disulfide B) Al2O3, dialuminum trioxide C) N2O4, dinitrogen tetroxide D) CCl4, carbon tetrachloride E) SCl2, sulfur dichloride
45.Which one of the following is named correctly?
A) ammonia, NH4+ B) calcium sulfide, Ca(HS)2 C) bromic acid, HBrO2 D) iron(III) oxide, FeO E) aluminum nitride, AlN
46.Which ionic formula is incorrect?
A) Fe(OH)2 B) CaCO3 C) Ca(ClO3)2 D) (NH4)2S E) K(NO3)2
47.Which of these acids has a name that begins with hydro-?
A) HClO B) HClO3 C) HClO4 D) HClO2 E) HCl
48.Elements belonging to which group of the periodic table form ions with a 2+ charge?
A) chalcogens B) alkaline earth metals C) halogens D) alkali metals E) alkaline metals
49.A certain metallic element forms a compound with chlorine, having the general formula XCl2. The X ion in this compound has 28 electrons. What is element X?
A) Zn B) V C) Fe D) Ni
Obviously this metallic element has +2 charge (knowing that Cl has -1 charge) and has 30 protons (the ion has 28 electrons after losing two electrons, so at neutral state it has 30 electrons, hence 30 protons). The element with proton number (or atomic number) is Zn.
50.Water, no matter where it is found, consists of hydrogen and oxygen combined in a 1:8 ratio by mass. This is a statement of
A)the law of conservation of mass
B)the law of multiple proportions
C)the law of conservation of energy
D)the law of constant composition
E)none of these
51.What is the best name for (NH4)2Cr2O7?
A) ammonium dichromate B) diammonium dichromium heptaoxide C) diammonium dichromate D) diammonium chromate E) ammonium chromate
52.An element has 17 protons, 18 electrons, and 20 neutrons. What isotope is it?
A) 3717Cl B) 3820Ca C) 3720Ca D) 3717Cl-
53.Which of the following are positively charged ions? (I) NH4; (II) ClO4; (III) SO4
A) III only B) I and II only C) none of these D) II only E) I only