Unit+I-III+Free+Response

__Concepts__
 * Unit I-III Free Response Test **
 * Formula Stoichiometry
 * Percent Composition
 * Empirical/Molecular Formulas
 * Chemical Reactions/Reaction Prediction
 * Reaction Stoichiometry
 * Conversions
 * Limiting Reactants
 * Electromagnetic Radiation
 * Electronic Configuration
 * Periodic Trends

__Possible Questions__ A compound containing the elements C, H, N, and O is analyzed. When a 1.2359 g sample is burned in excess oxygen, 2.241 g of CO2 (g) is formed. The combustion analysis also showed that the sample containing 0.0648 g of H. (i) Determine the mass, in grams, of C in the 1.2359 g sample of the compound. (ii) When the compound is analyzed for N content only, the mass percent of N is found to be 28.84 percent. Determine the mass, in grams, of N in the original 1.2359 g sample of the compound. (iii)Determine the mass, in grams, of O in the original 1.2359 g sample of the compound. (iv)Determine the empirical formula of the compound. Account for each of the following observations in terms of atomic theory and/or quantum theory. (a) Atomic size decreases from Na to Cl in the periodic table. (b) N/A (c) The first ionization energy of K is less than that of Na. (d) Each element displays a unique gas-phase emission spectrum. Answer the following questions about gases. (a) The average atomic mass of naturally occurring neon is 20.18 amu. These are two common isotopes of naturally occurring neon as indicated in the table below. (i) Using the information above, calculate the percent abundance of each isotope. (ii) Calculate the number of Ne-22 atoms in a 12.55 g sample of naturally occurring neon. (b) A major line in the emission spectrum of neon corresponds to a frequency of 4.34 x 1014 s-1. Calculate the wavelength, in nanometers, of light that corresponds to this line. (c) In the upper atmosphere, ozone molecules decompose as they absorb ultraviolet (UV) radiation, as shown by the equation below. Ozone serves to block harmful ultraviolet radiation that comes from the Sun.
 * 2006 Question 3a
 * 2006 Form B Questions 7
 * 2007 Form B Question 2
 * **Isotope** || **Mass (amu)** ||
 * Ne-20 || 19.99 ||
 * Ne-22 || 21.99 ||

A molecule of O3 (g) absorbs a photon with a frequency of 1.00 x 1015 s-1. (i) How much energy, in joules, does the O3 (g) molecule absorb per photon? (ii) The minimum energy needed to break an oxygen-oxygen bound in ozone is 387 kJ/mol. Does a photon with a frequency of 1.00 x 1015 s-1 have enough energy to break this bond? Support your answer with a calculation. Answer the following questions relating to gravimetric analysis. In the first of two experiments, a student is assigned the task of determining the number of moles of water in one mole of MgCl2∙nH2O. The student collects the data shown in the following table. (a) Explain why the student can correctly conclude that the hydrate was heated a sufficient number of times in the experiment. (b) Use the data to (i) calculate the total number of moles of water lost when the sample was heated, and (ii) determine the formula of the hydrated compound. (c) A different student heats the hydrate in an uncovered crucible, and some of the solid splatters out of the crucible. This splattering will have what effect on the calculated mass of the water lost by the hydrate? Justify your answer. In the second experiment, a student is given 2.94 g of a mixture containing anhydrous MgCl2 and KNO3. To determine the percentage by mass of MgCl2 in the mixture, the student uses excess AgNO3 (aq) to precipitate the chloride ion as AgCl (s). (d) Starting with the 2.94 g sample of the mixture dissolved in water, briefly describe the steps necessary to quantitatively determine the mass of the AgCl precipitate. Using principles of atomic and molecular structure and the information in the table below, answer the following questions about atomic fluorine, oxygen and xenon, as well as some of their compounds. (a) Write the equation for the ionization of atomic fluorine that requires 1681.0 kJ/mol. (b) Account for the fact that the first ionization energy of atomic fluorine is greater than that of atomic oxygen. (You must discuss __both__ atoms in your response.) (c) Predict whether the first ionization energy of atomic xenon is greater than, less than, or equal to the first ionization energy of atomic fluorine. Justify your prediction. A 0.150 g sample of solid lead (II) nitrate is added to 125 mL of 0.100 M sodium iodide solution. Assume no change in volume of the solution. The chemical reaction that takes place is represented by the following equation: Pb(NO3)2 (s) + 2 NaI (aq) → PbI2 (s) + 2 NaNO3 (aq) (a) List an appropriate observation that provides evidence of a chemical reaction between the two compounds. (b) Calculate the number of moles of each reactant. (c) Identify the limiting reactant. Show calculations to support your identification. (d) Calculate the molar concentration of NO3- (aq) in the mixture after the reaction is complete. (e) Circle the diagram below that best represents the results after the mixture reacts completely as possible. Explain the reasoning used in making your choice. A pure 14.85 g sample of the weak base ethylamine (C2H2NH2) is dissolved in enough distilled water to make 500 mL of solution. (a) Calculate the molar concentration of the C2H2NH2 in the solution. Methane gas reacts with chlorine gas to form dichloromethane and hydrogen chloride, as represented by the equation below: CH4 (g) + 2 Cl2 (g) → CH2Cl2 (g) + 2 HCl (g) (a) A 25.0 g sample of methane gas is placed in a reaction vessel containing 2.58 mol of Cl2 (g). (i) Identify the limiting reactant when the methane and chlorine gases are combined. Justify your answer with a calculation. (ii) Calculate the total number of moles of CH2Cl2 (g) in the container after the limiting reactant has been totally consumed.
 * 2008 Question 2
 * > Mass of empty container || 22.347 g ||
 * Initial mass of sample and container || 25.825 g ||
 * Mass of sample and container after first heating || 23.982 g ||
 * Mass of sample and container after second heating || 23.976 g ||
 * Mass of sample and container after third heating || 23.977 g ||
 * 2008 Question 5
 * **Atom** || **First Ionization Energy (kJ/mol)** ||
 * F || 1681.0 ||
 * O || 1313.9 ||
 * Xe || ? ||
 * 2008 Form B Question 3
 * 2009 Form B Question 1
 * 2009 Question 3


 * All answers to these questions can be found: [|http://apcentral.collegeboard.com/apc/public/exam/exam_information/1998.html#name08*]

Below are some reaction prediction practice questions. Look at the following questions: a-h, l, m, o, q, r, s, w, z, aa, cc, ee, jj, kk. Only look at the left column (ignore the right column). Hope this helps.