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Home , Isotopes of iridium

Exam 1 answer key 1. (5 points) , one of the coinage metals, has a melting point of 1084.62°C, while has a boiling point of –-320.43°F. What are these temperatures in Kelvin? 1084.62°C (1K/1°C) + 273.15K = 1357.77K

–320.43°F – 32°F = –352.43°F

–352.43°F 1°C = –195.79°C 1.8°F

-195.79°C (1K/1°C) + 273.15K = 77.36K

2. (3 points) Round of each of the numbers listed to the given number of significant figures and present the answer in the correct scientific notation. (There is no partial credit on this problem)

a. 1,600,961 (4 sig figs) 1.601x106

b. 195.71 (3 sig figs) 196 or 1.96x102

c. 0.001 265 982 (5 sig figs) 1.2660x10—3

3. (4 points) A certain substance is heated so that its temperature rises (changes) by 14°C. How many K (degrees Kelvin) does the temperature rise? Pick the appropriate answer and explain your answer. (No explanation, no credit)

a. 259 K b. –259 K c. 180K d. 14K e. 77 K 14°C is not the actual temperature. It represents a change in the temperature by 14°C which is a change of 14K. Although 1°C = 1K off set by 273.15, the change ∆T°C compare to the ∆TK means the offset is nullified.

4. (3 points) Predict the formula formed from the following pairs of elements. DO NOT NAME THE COMPOUND! (There is no partial credit on this problem)

a. Ba and O BaO

b. Li and N Li3N c. Mg and N Mg3N2 5. (9 points) Complete the following table

Isotopic Net charge symbol number number Protons Neutrons Electrons

Exam 1 Thursday February 22, 2018 Page 1 of 7

�� 77 199 77 122 77 0

�� � ���� 33 73 33 40 36 3–

��� � ���� 82 204 82 122 80 2+

6. (9 points) Which of the following is a chemical property of quinine and which is a physical property of quinine? Use [C] for chemical and [P] for physical.

a. __P__ The solubility of quinine is 1g quinine in 80 mL of benzene at a temperature of 25°C. b. __C__It is thought to bind to (react with) the DNA of a cell infected with Plasmodium falciparum, the malaria bug, inhibiting the cell’s ability to replicate.

c. __P_It melts at 177 °C.

d. __P__It is a white crystalline solid in pure form at room temperature.

e. __P__It has a molecular mass of 324.417amu

f. __C__Quinine yields dioxide and water vapor when burned.

7. (4 points) These values are not written in the most appropriate metric prefix. Re Write them please. Show the math and reasoning you used to support your answer.

a. 6.712 8 x 10—19 Tm (1 Tm = 1012m) 6.712 8 x 10—19 Tm 1012m 1µm = 0.67128 µ m = 0.67128 µ m 1Tm 10–6m

b. 8.965 561 x 107 pmol 8.965 561 x 107 pmol 10–12mol 1 µmol = 89.655 61 µ mol 1pmol 10–6mol c. 18.65 x 10—18 Mm2

18.65 x 10—18 Mm2 (106)2m2 1mm2 = 18.65 mm2 1Mm2 (10–3)2m2 8. (7 points) Differentiate between exact and inexact with a complete sentence (use space below) and indicate which of the following statements represent exact numbers (E) or inexact (I):

Exam 1 Thursday February 22, 2018 Page 2 of 7 a. __I___The length of the Mississippi River b. __I___The surface area of the moon c. __E___The number of pennies in a dollar d. __I___The volume of Lake Tahoe e. __E___The number of sheets of paper in a ream of paper.

ANSWER: EXACT: counted values or by definition; precise; infinite number of significant figures; no uncertainty INEXACT: measurement; precision based on tool; uncertainty; error.

9. (6 points) Perform the following calculation and report your answer with the correct significant figures and units. (Show your work for partial credit)

a. 2.171 012 1 g + 4.320 1 g + 401.278 77 g + 21.826 g 429.596g b. 2.156 934 51 x 1090 °C + 2.314 276 9 x 1091 °C + 2.954 681 211 x1093 °C 2.979 980 915 x1093 °C c. [10123 x 10—16]/ [10—18 x 1082] 1043

10. (5 points) Indicate the number of significant figures in each of the following measured quantities: (This problem has no partial credit)

a. 302400 km ___4__

b. 19.7324 Gmol __6___

c. 8.7300 mAmp __5___

d. 3024000.0 Tcd ___8__

e. 0.082 206 psec ___5__

Exam 1 Thursday February 22, 2018 Page 3 of 7

11. (3 points) Which of the following is an illustration of the law of constant composition? a. Water boils at 100°C at 1 atm pressure. b. Water is 11% and 89% by mass. c. Water can be separated into other substances by chemical means d. Water and salt have different boiling points. e. Water is a compound. Explain your choice with a complete sentence. Only(b) illustrates the Law of Constant Composition. In a given compound, the relative numbers and kinds of atoms are constant. This means the ratio of the of atoms in the formula is fixed and can’t change. Water has a 2:1 ratio of hydrogen to oxygen. This ratio can be represented by the percent composition by mass. The other parts of the problem refer to either physical or chemical properties of water such as the boiling point or a reaction.

12. As we learned in Chapters 1 & 13, the term ‘mixture’ refers to many different types of dispersions of materials (distribution of particles. Colloids are often classified as an intermediate type of dispersion. Answer the following as True (T) or False (F) about colloids. All of these statements are true for a colloid. a) Light scattering in a colloid system is known as the Tyndall effect ____

b) Milk is a colloidal suspension____

c) Colloids are considered heterogeneous mixtures, but have some qualities of homogeneous mixtures. ____

d) The difference between a true solution and a colloidal suspension is the size of the particles____

e) Whipped cream is formed by a dispersing a gas in a liquid. ____

13. (6 points) Classify each of the following as an element [E], a compound [C], or a mixture [M] a. __M__ A cup of coffee, no cream, no sugar b. __E__ Graphite c. __M__ Mud

d. __C__ Propane gas (CH3CH2CH3) e. __E__ Aluminum foil f. __E__ Liquid

g. __C__ K2C2O4

Exam 1 Thursday February 22, 2018 Page 4 of 7 14. (6 points) In Chapter 2, we studied the basic architecture of the atom. Answer the following by identifying the true and false statements. Correct the false statements and make then true. If the statement is true, give support for the answer. Use a complete sentence for full credit. They are all false!

a. The nucleus of an atom contains electrons and neutrons. [T] [F] The nucleus of an atom contains protons and neutrons.

b. Rutherford determined the charge to mass ratio of the electron. [T] [F] J.J. Thompson determined the charge to mass ratio of the electron

c. The nucleus of an atom can be positively or negatively charged depending on identity of the atom. [T] [F] The nucleus of an atom is always positively charged. Ions can be negatively or positively charged depending on the identity of the atom. The charge of the ion represents the difference between the number of protons and the number of electrons. The nucleus of the ion is positively charged (just like the atom from whence it came).

d. The charge of the neutron and the proton are equal but opposite in sign. [T] [F] The charge of the electron and the proton are equal but opposite in sign.

e. The number of neutrons in the nucleus is equal to the number of electrons outside of the nucleus. [T] [F] The number of protons in the nucleus is equal to the number of electrons outside of the nucleus in the neutral atom.

f. Millikan’s Foil experiment proved that the atom is mostly empty space. [T] [F] Rutherford’s gold foil experiment proved, among other points, that the atom is mostly empty space.

15. (5 points) Two of occur in nature: 1 has a mass of 190.961 amu and an abundance of 37.30% while isotope 2 has a mass of 192.963 amu and an abundance of 62.70%. Find the atomic mass of the element. 190.961 amu (0.3730) + 192.962amu (0.6270) = 192.2 amu

Exam 1 Thursday February 22, 2018 Page 5 of 7 16. (7 points) Give one example (atomic symbol and name) for each of the following: a) A transition element, which is ferromagnetic besides Fe. , Co or , Ni b) A reactive, pale yellow gas; the lightest of the : F, c) The main (representative) element in the third and 4th group: Si d) An in the fourth period K, e) An in the second period Be,

f) A solid diatomic: I, I2(okay) g) The whose Z is 54>Z>18 Kr, (sorry not kryptonite)

17. (5 points) Recently surfaced is " The Periodic Table of Rejected Elements," constructed by Gerber and Schwartz, noted table-ologists. There is something wrong with the name, the symbol or both. As a hint, they have included the atomic number, which is the only thing correct in this periodic table. Please correct the errors by writing BOTH the name and symbol. Architectural elements: 32 Cafetorium (Ct) Ge, 51 Auditorium (Ad) Sb, 34 Coliseum (Ci) Se, 80 Gymnasium (Gy) Hg, 48 Sanatorium (Sa) Cd,

18. (5 points) In Chapter 2 and 7, we are introduced to the periodic table. Answer the following by identifying the true and false statements. Correct the false statements and make then true by writing a complete sentence, not crossing out and repairing the answer. They are all false! a. Elements in a period have similar chemical properties [T] [F] Elements in a family have similar chemical properties b. Elements can be classified as either metalloids or non-metals. [T] [F] Elements are classified as metals or non- metals. c. The elements above the staircase are ductile, malleable, lustrous solids (for the most part) that are good conductors of heat. [T] [F] The elements BELOW the staircase are ductile, malleable, lustrous solids (for the most part) that are good conductors of heat d. is a metalloid. [T] [F] Gallium is below aluminum on the periodic table. It is a metal e. In the modern periodic table, the elements are arranged in order of increasing atomic mass. [T] [F] In the modern periodic table, the elements are arranged in order of increasing atomic mass.

Exam 1 Thursday February 22, 2018 Page 6 of 7 19. (6 points) Balance the following equations, for this question, if the coefficient is 1[one], put that in the line as well. You will lose points if you leave the lines blank:

a. ___4__BCl3 +__1___P4 +___6__H2® ___4__BP + __12___HCl

b. __1__C9H8O4 + __9__O2 ® __4__H2O + _9___CO2

c. __1__NCl3 + __3__H2O ®__1__NH3+_3___HOCl

d. __1__CaCO3 + __2__HCl ® __1__CaCl2 + __1__H2O + _1___CO2 e. Which of the reactions above represents a combustion? Explain your choice in one or two sentences. (2 points) Although (b) and (d) look similar, they are not both combustion reactions. For a combustion reaction to occur, one needs an organic compound and oxygen as a reactant. The product is always at least, carbon dioxide and water. Answer (d) does not have the correct reactants; even though carbon dioxide and water are produced, (d) does not meet the parameters of a combustion reaction.

20. (4 points) Passing an electric current through a certain substance produces oxygen and . Is this substance a compound, element, or a mixture? Explain your answer with one or two complete sentences. This is an example of a compound. Compounds are composed of two or more elements bonded together chemically. The process mentioned in the problem is a decomposition. The current breaks the chemical bonds to form the elements sulfur and oxygen. The substance is not a mixture, because mixtures are separated by physical means and each component of the mixture maintains its chemical and physical properties. The substance is not an element because elements can’t be broken down any further by chemical means.

21. (6 points) A package of aluminum foil contains 75.0 ft2 of foil, which weighs 12.6 oz. Aluminum has a density of 2.70 g/mL. What is the thickness of the foil in millimeters? 75.0 ft2 122in2 2.542cm2 69677.3cm2 1ft2 1in2

12.6 oz Al 28.35 g Al 1cm3 132.3 cm3 10 mm 0.0190 mm Oz 2.70g Al 69677.3 cm2 1 cm

22. Commando Cody and his Stratosphere Commandos protected our world from the flesh- eating zombies from outer space during the 1950’s. He patrolled the stratosphere every week. If the stratosphere (where he roamed) is 65,000 ft. above sea level, how high is this height in km? 65000ft 1 mi 1.6093 km 19.8 km 5280 ft 1 mi

Based on sf, 20. km

Exam 1 Thursday February 22, 2018 Page 7 of 7