CHEM 1A: Midterm Exam 1--Spring 2015 Name:_____________________________________________________ INSTRUCTIONS: On the FRONT and BACK of the scantron, fill out your name and 7-digit student ID. Fill in this information from left to right in the provided fields, and BUBBLE IN the values on the scantron. 1 point will be deducted from your exam grade for incomplete or erroneous filling of the scantron. MULTIPLE CHOICE QUESTIONS: 1. How many significant figures does this number have: 0.0005900 x 10-1 ? A. 2 B. 4 C. 5 D. 6 E. 8 2. The answer to the calculation below should be reported to how many significant figures? (ퟕퟓ.ퟗퟓퟎ−ퟕퟓ.ퟓퟓ) = ________ ퟕퟓ.ퟓퟓ A. 1 B. 2 C. 3 D. 4 E. 5 푱 3. Using dimensional analysis, simplify these units: = _______ (풎/풔)ퟐ A. kg·m2/s2 B. kg·m2/s C. kg·m/s2 D. kg·m/s E. kg 4. Convert 19.5 g·cm-3 to kg/m3. 10 3 A. 1.95 x 10 kg/m B. 1.95 x 105 kg/m3 C. 1.95 x 104 kg/m3 3 3 D. 1.95 x 10 kg/m E. None of the above. 5. Convert 36 x 10-6 mg to ng. A. 3.6 x 107 ng 1 B. 3.6 x 10 ng C. 3.6 x 10-11 ng D. 3.6 x 10-17 ng E. None of the above. 6. How many cubic micrometers (µm3) are in 1 cubic meter (m3)? A. 1 x 106 µm3 = 1 m3 B. 1 x 10-6 µm3 = 1 m3 C. 1 x 109 µm3 = 1 m3 D. 1 x 1018 µm3 = 1 m3 E. 1 x 10-18 µm3 = 1 m3 7. How many grams of nickel atoms are present in 4.42 moles of nickel metal (Ni)? Information that MIGHT be useful: Density of nickel = 8.908 g/cm3 A. 2.59 x 102 g B. 39.4 g C. 29.2 g D. 0.496 g E. 0.0750 g 8. How many TOTAL ATOMS are present in 0.878 moles of CH4? 3 Information that MIGHT be useful: Density of CH4 = 0.66 kg/m A. 1.06 x 1023 atoms B. 2.64 x 1024 atoms C. 1.32 x 1023 atoms D. 1.46 x 10-24 atoms E. None of the above 9. What is the volume (in cm3) of 453 mg of titanium metal? Information that MIGHT be useful: Density of titanium = 4.43 g/cm3 A. 0.102 g B. 2.01 g C. 4.89 g D. 9.78 g E. 21.7 g 10. How many molecules are present in 440 grams of carbon dioxide? A. 1.2 x 1027 B. 6.0 x 1024 molecules C. 1.8 x 1024 molecules 23 D. 6.0 x 10 molecules E. None of the above. 11. How many atoms are in 9.65 cm3 of gold (Au)? Information that MIGHT be useful: Density of gold = 19.3 g/cm3 A. 2.95 x 1022 atoms B. 5.69 x 1023 atoms C. 5.93 x 1025 atoms D. 6.11 x 1021 atoms E. 1.57 x 10-24 atoms 12. Which sample below contains the LEAST number of ATOMS? A. 4.00 g of diatomic hydrogen (H2) B. 4.00 g of helium C. 12.0 g of magnesium D. 44.0 grams of carbon dioxide E. All of the samples above contain the same number of atoms. 13. How do copper (I) and copper (II) differ? A. Different number of protons B. Different number of neutrons C. Different number of electrons D. Different atomic number E. Different masses 14. How do copper-63 and copper-65 differ? A. Different number of protons B. Different number of neutrons C. Different number of electrons D. Different atomic number E. Different charges 15. A substance is composed of 1.5999 grams oxygen and 0.7005 grams of an unknown element (X). Assuming the formula of this unknown substance is XO2 & using the relative masses, what is a possible identity of element X? A. Tungsten (W) B. Tin (Sn) C. Titanium (Ti) D. Sulfur (S) E. Nitrogen (N) 16. Naturally occurring Strontium (Sr) consists of the four stable isotopes below and has an average atomic mass of 87.62 amu. Based on only this data, select the isotope that is MOST abundant, or choose E. if insufficient information is provided to make a conclusion. Strontium Isotope Isotopic Mass (amu) A. Strontium-84 83.9134 B. Strontium-86 85.9092 C. Strontium-87 86.9088 D. Strontium-88 87.9056 E. Cannot determine from information provided. 17. Naturally occurring Chromium (Cr) consists of the four stable isotopes below and has an average atomic mass of 52.00 amu. Based on only this data, select the isotope that is MOST abundant, or choose E. if insufficient information is provided to make a conclusion. Chromium Isotope Isotopic Mass (amu) A. Chromium-50 49.9460 B. Chromium-52 51.9405 C. Chromium-53 52.9406 D. Chromium-54 53.9389 E. Cannot determine from information provided. 18. Naturally occurring Cerium (Ce) consists of the four stable isotopes below and has an average atomic mass of 140.12 amu. Based on the fact that Cerium-140 is the most abundant of these four isotopes (with a percent abundance of 88.45%), which isotope must be the SECOND most abundant? Select E. if insufficient information is provided to make a conclusion. Cerium Isotope Isotopic Mass (amu) MOST ABUNDANT Cerium-140 139.9054 A. Cerium-136 135.9072 B. Cerium-138 137.9060 C. Cerium-142 141.9092 D. Ce-136 & Ce-138 are tied for the second most abundant isotopes of Cerium. E. Cannot determine from information provided. 19. Which form of radiation is LEAST penetrating? A. Alpha (α) particles B. Normal beta (β-) particles C. Gamma (γ) rays D. B & C are equally penetrating. E. All of the above are equally penetrating. 232 20. What final isotope would be produced if Thorium-232 ( 90푇ℎ) underwent one alpha decay, followed by one beta decay, followed by one gamma decay? A. Radium-228 B. Francium-227 C. Radon-230 D. Actinium-228 E. None of the above. 21. Which pair reacts to form ionic compounds? A. Potassium (K) and Beryllium (Be) B. Iron (Fe) and Osmium (Os) C. Nitrogen (N) and Oxygen (O) D. Copper (Cu) & Selenium (Se) E. None of the above would form ionic compounds. 22. Which pair reacts to form covalent compounds? A. Lithium (Li) and Fluorine (F) B. Bromine (Br) & Sulfur (S) C. Barium (Ba) and Thallium (Tl) D. Indium (In) and Tellurium (Te) E. None of the above would form covalent compounds. 23. What must the charge on X be in the ionic compound: X(CrO4)3? A. +1 B. +2 C. +3 D. +4 E. +6 24. Consider the formula of aluminum sorosilicate as Al2Si2O7. Based on this information, what is the charge (x) on x one of the polyatomic ions, sorosilicate: Si2O7 ? A. x = -2 B. x = -3 C. x = -4 D. x = -6 E. x = -14 25. What is the approximate molar mass of (NH4)2SO4 to three significant figures? A. 160. g/mol B. 132 g/mol C. 118 g/mol D. 114 g/mol E. None of the above. 26. Which electron transition below would emit the SHORTEST wavelength of light? (where ni is the initial state and nf is the final state) A. ni = 10 → nf = 2 B. ni = 10 → nf = 4 C. ni = 4 → nf = 10 D. ni = 4 → nf = 2 E. ni = 2 → nf = 4 27. Consider the two electromagnetic waves shown to the 15 right. If the top wave has a frequency of 9.5 x 10 Hz, how would the bottom wave compare? A. The bottom wave would have a longer wavelength. B. The bottom wave would have the same wavelength. C. The bottom wave would have a lower frequency. D. The bottom wave would have a higher frequency. E. The bottom wave would have the same frequency. 28. What is the frequency of light emitted from a laser beam operating at 532 nm? A. 1770 Hz B. 5.64 Hz C. 0.000564 Hz 14 -1 D. 5.64 x 10 s E. 1.77 x 10-15 /s 29. Assume that light of 950 nm is NOT capable of ejecting electrons from the surface of a metal. What would light at 925 nm do? A. It also will NOT cause electrons to be ejected. B. It WILL cause electrons to be ejected. C. Cause a transition from ni = 10 → nf = 3 D. Cause a transition from ni = 3 → nf = 10 E. Cannot determine from information provided. The work function of the metal would need to be specified. 30. Four different unknown metals (1, 2, 3, & 4) were exposed to light of the SAME wavelength. Given the work function of each metal below, which metal would eject electrons with the LOWEST velocity? A. Metal 1: Ф = 612 kJ/mol B. Metal 2: Ф = 472 kJ/mol C. Metal 3: Ф = 987 kJ/mol D. Metal 4: Ф = 504 kJ/mol E. Cannot determine from information provided. 31. The energy required to eject an electron from an unknown metal is Ф = 3.31 x 10-20 J/electron. Calculate the MAXIMUM wavelength of light that can eject an electron from this metal. A. 6.00 x 10-6 m B. 1.67 x 1021 m C. 6.00 x 10-22 m D. 1.67 x 105 m E.