I. (40 points) A. (14 points) Fill in the empty boxes with the appropriate symbol, number, word or charge. Nuclear symbol 39 K 58 Ni 2+ Protons 28 30 8 (name of subatomic particle) Electrons 10 Mass Number 16 Atomic Number Net Charge 0 2 1
B. (6 points) Determine whether the statements given below are true or false. Write Y if the statement is true, and N if the statement is false in the blanks provided. Do not usetorf. 1. Neutrons have neither mass nor charge. 2. Isotopes of an element have an identical number of protons. 3. C 14 and N 14 have identical neutron to proton (n/p + ) ratios. 4. The vertical columns in a periodic table are referred to as groups. 5. When an atom loses an electron, it becomes positively charged. 6. An anion is a negatively charged ion. C. (10 points) Write the formulas of the following compounds. 1. Carbon dioxide 2. dinitrogen pentoxide 3. hydrogen peroxide 4. manganese(ii) fluoride 5. potassium chlorite D. (10 points) Write the names of the following compounds: 1. HBr (g) 2. NH 3 3. P 4 S 10 4. Fe(NO 3 ) 3 5. KClO 4 2
II. (25 points) SHOW ALL WORK IN A LOGICAL WAY in the space provided. Work done elsewhere will not be considered. Answers without work, no matter how trivial the problem may seem, will receive no credit. Place your answers in the blank provided. Use appropriate units and significant figures throughout. A. The metric prefix micro (µ) represents the factor 10 6. How many µm are there in one cm? B. The solubility of table sugar (sucrose) in water at 20 Cis2.10x10 2 g sucrose/100 g of water. If 55.0 g of sugar were added to 20.0 g of water at 20 C, how many grams of sugar would remain undissolved? 3
C. A solution is prepared from 25.0 ml of ethyl alcohol (d = 0.780 g/ml) and 35.0 ml of water (d = 1.00 g/ml). The volume of the solution is 58.0 ml. 1. What is the density of the solution? 2. What is the mass percent of ethyl alcohol in the solution? D. The area of the 48 contiguous states is 3.02 x 10 6 mi 2. Assume that these states are completely flat (no mountains and no valleys). What volume of water, in liters, would cover these states with a rainfall of two inches? 1 ft 3 = 28.32 L and 5280 ft =1mi. 4
III. (60 points) A. (15 points) Answer the questions below, using LT (for is less than), GT (for is greater than), EQ (for is equal to), ormi (for more information required) in the blanks provided. 1. The mass (to 3 significant figures) of 6.022 x 10 23 atoms of Na (1) 23.0 g. 2. Boron has 2 isotopes, B 10 (10.01 amu) and B 11 (11.01 amu). The abundance of B 10 (2) the abundance of B 11. 3. If S 32 were assigned as the standard for expressing relative atomic masses and assigned an atomic mass of 10.00 amu, the atomic mass for H would be (3) 1.00 amu 4. When phosphine gas, PH 3, is burned in oxygen, tetraphosphorus decaoxide and steam are formed. In the balanced equation (using smallest whole number coefficients) for the reaction, the sum of the coefficients on the reactant side is (4) 7. 5. The mass (in grams) of one mole of bromine molecules is (5) 79.90. B. (5 points) An oxide of titanium is made up titanium (Ti) and oxygen atoms. It is determined that the oxide is 40.06% oxygen. What is the simplest formula for the oxide? 5
C. (20 points) Consider hydrazine, N 2 H 4. 1. What is its molar mass in grams? 2. What is its simplest formula? 3. How many moles are there in 2.65 g of hydrazine? 4. How many grams of hydrazine are there in 12.01 x 10 26 molecules of hydrazine? 5. How many hydrogen atoms are there in 1.769 mol of hydrazine? 6. How many grams of hydrogen can be obtained from 100.0 g of hydrazine? 6
D. (8 points) For the reaction 3Br 2 (l) +I 2 (s) 2 IBr 3 (s) How many grams of IBr 3 (M = 366.6 g/mol) can be obtained from 5.00 g of Br 2 (M = 159.8 g/mol)? E. (12 points) Consider the following reaction. 2BF 3 (aq) + 3 H 2 O (g) B 2 O 3 (s) + 6 HF (g) In an experiment 7.2 mol of BF 3 reacts with 8.9 mol of H 2 O. 1. What is the theoretical yield of B 2 O 3 (in moles)? (Assume 100% yield.) 2. How many moles of the excess reactant remain? (Assume 100% yield.) 3. If the reaction has a 73% yield, what is the actual yield of B 2 O 3 (in moles)? 7
IV. (25points) A. (15 points) In each of these questions, PRINT in capital letters (i.e. A, B, C, etc. and not a, b, c, etc.) on the blanks at the left the letter of that choice which is the best answer. Circled letters will not be considered. There is no penalty for guessing. Answer the following questions by referring to the graph of the solubility data for CuSO 4 5H 2 O and KNO 3 printed on a sheet at the back of this exam. You may tear out that sheet. Consider a solution formed with 50.0 g of CuSO 4 5H 2 O, 50.0 g of KNO 3 and only 50.0 g of water. 1. The solution is heated to 60 C. Choose the statement that best describes this solution: A. This is a clear solution. B. This is a cloudy solution. C. This is a clear solution with only CuSO 4 5H 2 O crystals forming on the bottom. D. This is a clear solution with only KNO 3 crystals forming on the bottom. E. Crystals of both salts form. 2. The solution is cooled to 25 C. Choose the statement that best describes this solution: A. This is a clear solution. B. This is a cloudy solution. C. This is a clear solution with only CuSO 4 5H 2 O crystals forming on the bottom. D. This is a clear solution with only KNO 3 crystals forming on the bottom. E. More crystals are formed from CuSO 4 5H 2 O than from KNO 3. F. None of the above is true. 3. Fifty grams of KNO 3 are added to the original solution to bring the total composition to 100.0 g KNO 3, 50.0 g CuSO 4 5H 2 O and 50.0 g of water. The solution is heated to 85 C. Choose the statement that best describes this solution: A. This is a clear solution. B. This is a cloudy solution. C. This is a clear solution with only CuSO 4 5H 2 O crystals forming on the bottom. D. This is a clear solution with only KNO 3 crystals forming on the bottom. E. More crystals are formed from KNO 3 than from CuSO 4 5H 2 O. F. None of the above is true. 8
B. (5 points) Write the answers on the blanks provided on the left. (1) What is the name of the value in chromatography obtained in the following way: distance traveled by ion/distance traveled by solvent (2) What is the color of CuSO 4 5H 2 O? (3) What is the color of SiC? (4) What is the name of the special flask used in the density experiment? (5) What is the name of the funnel used to fiter a solution using a vacuum line? C. (5 points) A sample of an alloy is placed in a flask with a volume of 50.00 ml. The flask weighs 57.0234 grams empty. The flask weighs 86.7894 g when weighed with the alloy. The flask + alloy + water weighs 120.8604 g. Take the density of water to be 1.000 g/ml. What is the density of the alloy? 9
BONUS (15 points) All or nothing. The bonus should be done only after you have completed the main part of this exam and checked your work for errors. The time alloted for this exam does not include time for the bonus. Consider 45.00 g of a saturated solution at 30 C made up of salt Y and water. The solution contains the maximum amount of salt that can be dissolved. The solubility of salt Y in water at 30 C is 22.04 g Y/100 g water. How much water is present in the solution? 10