Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Rutherford backscattering spectrometry wikipedia , lookup
Physical organic chemistry wikipedia , lookup
Transition state theory wikipedia , lookup
State of matter wikipedia , lookup
Van der Waals equation wikipedia , lookup
Degenerate matter wikipedia , lookup
Vapor–liquid equilibrium wikipedia , lookup
Equation of state wikipedia , lookup
CHEMISTRY 1127 Name FINAL EXAMINATION ______________________ Signature December 14, 2013 Section _____________________ ______________________ TA ______________________ PLEASE READ THE FOLLOWING INSTRUCTIONS Do NOT begin the exam until asked to do so. There are 12 numbered pages in this exam. Check to see they are all here before you begin the exam. Return all these papers when you are finished. A separate packet has a page of equations, a periodic table, and a phase diagram. Make sure that you have both packets. Use a pen with blue or black ink for the entire exam. Be sure to follow ALL directions. In working the problems, you MUST SHOW ALL WORK. Write your answers in the space provided. Use correct significant figures and units throughout. No credit will be given unless all work is clearly shown and the method of solution is logically correct. For those who have an excused absence from an hourly exam, and are using part of this final as credit for that exam: Part I corresponds to Exam I. Part II corresponds to Exam II. Part III corresponds to Exam III You may want to spend extra time on the particular portion of this exam that corresponds to the hourly exam that you missed. Page Total 1 Page Total ____________ / 37 7 ____________ / 28 2 ____________ / 15 8 ____________ / 16 3 ____________ / 21 9 ____________ / 16 4 ____________ / 28 10 ____________ / 8 5 ____________ / 19 11 ____________ / 29 6 ____________ / 12 12 ____________ / 20 TOTAL : Grader Grader CHEM 1127, Final Exam December 14, 2013 Name _______________________ I. (74 points) A. (15 points) Answer the following questions on the blanks provided. _______________ 1. A solution is made up of 12.0 g of sugar and 112 g of water. What is the mass % of sugar in the solution? _______________ 2. How many grams of water are required to dissolve a mixture made up of 28 g of A (solubility = 14 g/100 g H2O) and 28 g of B (solubility = 25 g/100 g H2O)? _______________ 3. What is the molar mass of Na2CO3.10H2O? _______________ 4. What is the mass percent of oxygen in CaCO3? _______________ 5. The edge of a cube, made up of an alloy is 2.00 cm. The cube has a mass of 12.0 g. What is the density of the alloy? B. (18 points) Answer the following questions by writing your answers on the blanks provided. _______________ 1. Write the chemical formula of sodium chlorite? _______________ 2. Write the chemical formula of iron(III) carbonate? _______________ 3. What is the name of the compound HNO2 (aq)? _______________ 4. What is the name of the compound CH4? _______________ 5. Write the chemical formula of silver sulfate? _______________ 6. What is the name of the compound N2O5? Consider nuclear symbol of nickel ion which is given as answers in the blanks provided. C. 60 28 _______________ 7. How many protons are there? _______________ 8. How many electrons are there? Ni 2+ to answer questions 7 - 9 Write your _______________ 9. How many neutrons are there? (5 points) A solution is prepared using 10.00 mL chloroform (d =1.492 g/cm3) and 10.00 mL of benzene (d = 0.879 g/cm3). What is the density of the final solution? (Volumes are additive) ____________________ 1 CHEM 1127, Final Exam December 14, 2013 D. Name _______________________ (5 points) An element has three naturally occurring isotopes with the following abundances and masses: Abundance mass (amu) 90.48% 19.992440 0.27% 20.993846 9.25% 21.991385 Determine the molar mass of the element. ____________________ E. (8 points) In each of these questions, PRINT, in capital letters (i.e. A, B, C, etc. and not a, b, c, etc.) in the blanks the letter corresponding to the best answer. Circled letters will not be considered. There is no penalty for guessing. ________ 1. The element found in Group 3, Period 4 in the periodic table is A) Ga B) Na C) Sc D) K E) None of the above ________ 2. Which of the following is not a metallic element? A) Sc B) F C) Ag D) Cu E) Zn ________ 3. Which of the following can be considered a simplest formula? A) K2Cr2O4 B) H3P3O3 C) N2O4 D) C2H6 E) KMnO4 ________ 4. Consider a solution of ethyl alcohol and water. Ethyl alcohol is completely soluble in water. The combination is best described as A. B. C. D. E. E. A heterogeneous mixture A homogeneous compound A pure element A homogeneous mixture None of the above (2 points) Balance the following equation using the smallest whole numbers as stoichiometric coefficients. Calculate the sum of the coefficients of the reactants and the products? C2H2 (g) + O2 (g) → CO2 (g) + H2O (ℓ) ____________________ 2 CHEM 1127, Final Exam December 14, 2013 F. (4 points) What is the mass (in grams) of a tin (Sn) atom? G. Name _______________________ ____________________ (5 points) Magnesium atoms react with bromine in a ratio of 1 atom to 2 atoms respectively according to the following reaction. Mg (s) + Br2 (ℓ) → MgBr2 (s) If 1.00 g of magnesium reacts with 10.0 g of Br2, how many grams of product are produced? H. ____________________ (8 points) An Erlenmeyer flask contains 125.0 mL of a solution of 0.450 M CoCℓ3. 1.How many moles of chloride ions are present? ____________________ 2.What volume of 0.450 M CoCℓ3 must be taken to obtain 0.00250 mol of Co3+ ions? ____________________ I. (4 points) Polyethylene is a polymer consisting of only carbon and hydrogen. If 2.300 g of the polymer is burned in oxygen it produces 2.955 g H2O and 7.217 g CO2. What is the empirical formula of polyethylene? (Circle the correct answer) A. CH B. CH2 C. C2H3 3 D. C5H8 E. C7H8 CHEM 1127, Final Exam December 14, 2013 Name _______________________ II. (59 points) A. (6 points) Write the appropriate letter in the blank provided. _______ 1. What volume of CH4 at 0°C and 1.00 atm contains the same number of molecules as 0.50 L of N2 measured at 27°C and 1.50 atm? A. 0.37 L B. 0.46 L C. 0.50 L D. 0.82 L E. 0.68 L _______ 2. At 25ºC, a molecule of pentane, C5H12, effuses more slowly than a molecule of propane, C3H8. This is principally because, A. pentane is heavier than propane. B. pentane has more H atoms. C. rate and effusion are directly proportional D. at 25ºC, the kinetic energy of pentane is smaller than the kinetic energy of propane. _______ 3. Which of the following is insoluble in water? B. C. A. KNO3 B. CuSO4 C. NaOH D. HCℓ E. BaSO4 (12 points) Write the products obtained when aqueous solutions of the following compounds react. If there is not any reaction between the species write NR. Do not include the spectator ions, or you will lose points. 1. HF and NaOH _____________________________ 2. CuCl2 and Na2SO4 _____________________________ 3. NH3 and NaOH _____________________________ 4. CH3NH2 and HBr _____________________________ (10 points) Consider the reaction between K2S and CoCℓ3 for the following two questions. 2Co3+ (aq) + 3S2- (aq) → Co2S3 (s) 1. How many moles of K2S are required to react completely with 0.125 moles of CoCℓ3? ____________________ 2. Calculate the mass of Co2S3 that forms from the reaction of 0.125 moles of CoCℓ3 with 1000.0 mL of 0.100 M K2S. ____________________ 4 CHEM 1127, Final Exam December 14, 2013 Name _______________________ C. (14 points) Write your answer in the blank provided. Examine the following balanced half-reaction: 2H2O + CrO2- → CrO42- + 3e- + 4H+ __________ 1. (2 points) Is this an oxidation or a reduction? __________ 2. (2 points) What element is oxidized or reduced? Balance the following half-equation in acid. ClO3 → Cl2 __________ 3. (4 points) What is the coefficient of H+ in your balanced equation? The above reaction occurs along with the reaction given above before Part 1 of this problem. Write a balanced equation for the overall reaction that occurs. __________ 4. (4 points) What is the coefficient of water in the balanced overall equation? __________ 5. (2 points) Which reactant is the oxidizing agent? D. (5 points) Hydrogen gas bubbled into a solution of barium hydroxide that has sulfur in it. The balanced equation for the reaction that takes place is 2OH-(aq) + H2(g) + S(s) S2-(aq) + 2H2O What volume of 0.350 M of Ba(OH)2 is required to react completely with 2.50 g of sulfur? ____________________ 5 CHEM 1127, Final Exam December 14, 2013 E. Name _______________________ (12 points) Consider oxygen gas: 1. A 6.00 L flask contains oxygen gas at a certain temperature and pressure. What is the volume of a flask that would contain the same amount of oxygen gas at a pressure twice that of the original pressure and a temperature, a third that of the original temperature in K. ____________________ 2. A certain amount of oxygen gas effuses out of a pinhole in 45 seconds. How long will it take for the same amount of N2O4 to effuse out of the same pinhole? ____________________ 3. Oxygen gas is a product of the electrolysis of Aℓ2O3 2Aℓ2O3 (s) → 4Aℓ (s) + 3O2 (g) What volume of oxygen gas measured at 25ºC and 1.00 atm is produced from the electrolysis of 1.000 x 103 kg (1 metric ton) of Al2O3? ____________________ 6 CHEM 1127, Final Exam December 14, 2013 Name _______________________ III. (68 points) A. (10 points) Answer the following questions, using Y if the statement is true and N if the statement is false. Write your answers in the blanks provided. _________ 1. A molecule that follows the octet rule has a central atom and 4 surrounding atoms. The geometry must be tetrahedral. _________ 2. A photon’s energy is directly proportional to its wavelength. _________ 3. In the hydrogen atom a transition from n = 2 to n = 3 requires the same amount of energy as a transition from n = 3 to n = 4. _________ 4. For the following reaction, ΔH° = ΔHf° for CH3OH (ℓ): 2 C (s) + 4H2 (g) + O2 (g) → 2CH3OH (ℓ) _________ 5. At constant pressure ΔHsystem + ΔHsurroundings = 0 B. (8 points) Write your answers in the blanks provided: 1. What is the abbreviated ground state electron configuration for Mn? ________________________ _________ 2. How many unpaired electrons are there in Mn3+? _________ 3. How many electrons can an atom have with quantum numbers n=5, ℓ= 3, mℓ= +2. _________ 4. What element has the abbreviated electron configuration of [Kr]5s2 4d6? C. (6 points) Write your answers to the blanks provided. Consider the atoms: Na, Si, Rb, and Sn. _________ 1. Which atom is the smallest? _________ 2. Which atom has the highest first ionization energy? _________ 3. Which atom has the lowest electronegativity? D. (4 points) How much energy is associated with a transition from n = 10 to n = 5? __________________ In this transition is energy absorbed or given off? _____________ 7 CHEM 1127, Final Exam December 14, 2013 E. Name _______________________ (6 points) Write the Lewis structure of each of the following species in the box provided and the molecular geometry in the blank provided. 1. IO4Lewis Structure: Molecular geometry: ____________________ 2. NO3Lewis structure: Molecular geometry: ____________________ (10 points) SeCl4 has the following Lewis structure. Using the Lewis structure given answer the questions below. : :Cl : Cl : : : Se : : : F. : :Cl : Cl : ___________ 1. What is the total number of valence electrons? ___________ 2. What is the hybridization of the central atom? ___________ 3. What is the molecular geometry? ___________ 4. Is the molecule polar or nonpolar ___________ 5. What is the formal charge on the central atom? 8 CHEM 1127, Final Exam December 14, 2013 G. (8 points) Consider the following thermochemical data: 2P (s) + 3Cℓ2 (g) → 2PCℓ3 (ℓ) PCℓ3 (ℓ) + Cℓ2 (g) → PCℓ5 (s) Name _______________________ ΔH° = -636 kJ ΔH° = -138 kJ 1. Write a balanced chemical equation for the formation of one mole of PCℓ5 (s) from its elements. ________________________ 2. Calculate ΔHf° for PCℓ5 (s). ________________________ H. (8 points) Using the data provided below answer the following questions. Specific heat for bromine ΔHvap° for bromine Boiling point 0.474 J/g⋅°C 29.6 kJ/mol 59.0 °C 1. Calculate ΔH for 15.0 g Br2 (ℓ, 22.5 °C) → Br2 (ℓ, 59.0 °C) _____________________ 2. Calculate ΔH for 15.0 g of Br2 (ℓ, 59.0 °C) → Br2 (g, 59.0 °C) ____________________ 9 CHEM 1127, Final Exam December 14, 2013 I. Name _______________________ (8 points) The thermochemical equation for the preparation of NH3 from a reaction between HNO3 and hydrogen gas is given below. HNO3 (g) + 4H2 (g) → NH3 (g) + 3H2O (g) ∆H = -637 kJ 1. Calculate ∆H when one mol of hydrogen gas reacts. ____________________ 2. What is ∆H when 10.00 g of NH3 (g) is made to react with an excess of steam to form HNO3 and H2 gases? _________________________ 10 CHEM 1127, Final Exam December 14, 2013 Name _______________________ IV. (49 points) A. (8 points) Answer the questions below, using LT (for is less than), GT (for is greater than), EQ (for is equal to), or MI (for more information required) in the blanks provided. _________ 1. The boiling point of NH3 _ the boiling point of CH4. _________ 2. The vapor pressure of compound X is 250 mm Hg at 57°C. Given a sealed flask that contains some liquid X, the vapor pressure in the flask _ _ 250 mm Hg. _________ 3. The density of Y (ℓ) is 1.2 g/mL while that of Y (s) is 0.95 g/mL. the melting point of Y at 1 atm pressure __ the melting point of Y at 10 atm pressure. _________ 4. Compound A has a vapor pressure of 760 mm Hg at 85°C. Compound B has a vapor pressure of 760 mm Hg at 40°C. The boiling point of B _ boiling point of A. B. (16 points) Fill in the blanks. ____________ 1. Do dispersion forces exist in all molecules? ____________ 2. Dispersion forces (increase, decrease, do not change) when molar mass increases. ____________ 3. What intermolecular force(s) is/are present in water? ____________ 4. Which has a higher boiling point, CH4 or CCl4? For the next four questions, identify the compounds as ionic, molecular, network covalent, or metallic. ____________ 5. C (graphite) ____________ 6. W ____________ 7. KF ____________ 8. HF C. (5 points) Acetic acid has a heat of vaporization of 23.7 kJ/mol. At 35°C, acetic acid has a vapor pressure of 106 mm Hg. What is the boiling point temperature of acetic acid at 760 mm Hg? _______________ 11 CHEM 1127, Final Exam Name _______________________ December 14, 2013 D. (6 points) Consider 20.0 g of CHCl3 (MM = 119 g/mol) at 45°C (vapor pressure = 448 mm Hg) in a sealed 5.00 L flask. 1. What is the pressure in the flask? _______________ 2. What is/are the physical state(s) present in the flask? _______________ E. (14 points) Consider the phase diagram for CCℓ4 below. Answer the questions about the diagram by writing your answers on the blanks provided. __________ 1. Point A represents an equilibrium between _____ phases. __________ 2. What is CCℓ4 at point C called? __________ 3. Does the boiling point increase as pressure above the liquid is decreased? (yes or no) __________ 4. What point represents CCℓ4 only in the gas phase? __________ 5. Does the melting point increase as pressure is applied to the solid? __________ 6. Is the density of liquid is higher than the density of the solid? __________ 7. Define the phase change going from point B to C. 12