Chemistry Semester Exam Answer Key

A chemical reaction involving substances A and B stops when B is completely used. B is the Select one: a. limiting reactant. ANSWER b. primary product. c. excess reactant. d. primary reactant. Match each description below with the term that best fits it. The phase change from liquid to solid The phase change from liquid to gas that occurs at the surface of a liquid, often well below the liquid's vaporization temperature The phase change from liquid to gas that occurs within a liquid when the liquid is at its vaporization temperature The phase change from gas to liquid The phase change from solid to liquid The phase change from solid directly to gas, without a change to liquid Freezing Evaporation boiling Condensation melting Sublimation Which of the following diatomic elements has a double bond between its atoms? Select one: nitrogen chlorine fluorine hydrogen oxygen ANSWER Identify each of the following statements as describing a synthesis, single displacement, decomposition, or double displacement reaction. takes place between two ionic compounds Double displacement only has one reactant Decomposition reactants are an element and a compound and the Single displacement products are a new compound and a different element two or more substances react to form a single product Synthesis Calcium carbide (CaC2) reacts with water to produce acetylene (C2H2): CaC2 (s) + 2H2O (g) → Ca(OH)2 (s) + C2H2 (g) Production of 13 g of C2H2 requires consumption of __________ g of H2O. Select one: 4.8 × 10-2 18 ANSWER 4.8 × 102 9.0 4.5 The pressure in a 12.2 L vessel that contains 2.34 g of carbon dioxide, 1.73 g of sulfur dioxide, and 3.33 g of argon, all at 42°C is __________ mm Hg. Select one: a. 134 b. 263ANSWER c. 395 d. 0.347 e. 116 How many grams of calcium chloride would form if 1.25 liters of a 2.50 molar hydrochloric acid (HCl) solution reacts with 1.10 liters of a 2.25 molar calcium hydroxide Ca(OH)2 solution? 2HCl (aq) + Ca(OH)2 (aq) = CaCl2 (aq) + H2O (l) Select one: a. 429 g b. 858 g c. 173 g ANSWER d. 275 g Because excited hydrogen atoms always produce the same line-emission spectrum, scientists concluded that hydrogen Select one: could only exist in the ground state. did not release photons. released photons of only certain energies. ANSWER had no electrons. How does increasing the temperature change the solubility of carbon dioxide in water? Select one: More information is needed to determine the effect. The solubility would decrease. ANSWER The solubility would not change. The solubility would increase. What volume (L) of NH3 gas at STP is produced by the complete reaction of 7.5 g of H2O according to the following reaction? Mg3N2 (s) + 6H2O (l) → 3Mg(OH)2 (aq) + 2NH3 (g) Select one: 19 28 3.1 ANSWER 9.3 0.32 The atom with the same number of neutrons as 12C is Select one: 11B. ANSWER 14N. 13C. 9Be. A balloon has a volume of 1.2 liters at 27.4 C. The balloon is then heated to a temperature of 167.3 C. What is the volume (in liters) of the balloon after heating? ANSWER= 1.76 L Mrs. Born wants to figure out if watering seeds with different amounts of water will cause them to grow differently. She keeps all of the seeds the same distance from the window in containers with the same type and amount of soil. She also waters them all with tap water from the sink. The only thing she changes is the amount of water she gives them. After 10 days she measures their height. Which of the following best describes the role of the amount of water each plant gets in the experiment? Select one: independent variable hypothesis dependent variable control Which of the following elements has two (2) valence electrons? Select one: Al S Na Mg ANSWER How many moles of atoms are in 750 mg of phosphorus? (Keep in mind: you are given mg as your starting unit!) Select one: a. 0.024 moles b. 24.2 moles c. 23.2 moles You need to divide by the molecular weight, rather than multiplying by it. d. 0.074 moles Determine the empirical formula of a sample that has: 85.7% carbon(C) and 14.3% hydrogen(H)? ANSWER: CH2 If you dilute 20 mL of a 1 M NaOH stock solution with 30 mL of water, what is the molarity of your diluted solution? Select one: a. 0.6 M b. 0.5 M c. 0.7 M d. 0.3 M e. 0.4 M ANSWER Which of these can happen due to decreasing the average energy of a liquids particles? Select one: a. vaporization b. evaporation c. a random arrangement d.Freezing ANSWER If the reaction of 9.87 moles of potassium with excess hydrobromic acid produced a 79.8% yield of hydrogen gas, what was the actual yield of hydrogen gas? Unbalanced equation: K + HBr → KBr + H2 Select one: 3.94 mol H2 ANSWER 5.74 mol H2 7.88 mol H2 4.94 mol H2 Calculate the percentage by mass of oxygen in Pb(NO3)2. Select one: a. 14.5 b. 9.7 c. 29.0 ANSWER d. 33.4 e. 19.3 When water is warmed from its freezing temperature to its temperature of maximum density, it Select one: a. maintains a constant volume. b. expands. c. contracts. ANSWER d. increases in weight. How many molecules are there in 5.0 g of methyl alcohol, CH3OH? Select one: 9.4 x 1022 ANSWER 3.8 x 1024 3.0 x 1024 3.6 x 1024 Which of the following statements is not true regarding acids? Select one: a. Acids can be both highly and mildly corrosive. b. Most fruits contain weak acids. c. Active metals will react with acids in double replacement reactions. ANSWER d. Acids react with bases in neutralization reactions to produce water. Calculate the concentration (in M) of hydronium ions in a solution at 25.0 °C with a pOH of 4.223. Select one: a. 5.99 × 10-19 b. 1.67 × 10-10 ANSWER c. 1.67 × 104 d. 1.00 × 10-7 e. 5.98 × 10-5 The liquid state of matter can be described as having a definite volume but not a definite shape. ANSWER having lost electrons owing to energy content. having definite shape and definite volume. having neither a definite shape nor a definite volume. There are __________ mol of bromide ions in 0.500 L of a 0.300 M solution of AlBr 3. Select one: a. 0.0500 b. 0.150 c. 0.167 d. 0.500 e. 0.450 ANSWER According to the kinetic-molecular theory, how does a gas expand? Select one: Collisions between particles become elastic. Its particles become larger. Its temperature rises. Its particles move greater distances. ANSWER Which of the following aqueous solutions has the highest [OH-]? Select one: a solution with a pOH of 12.0 pure water ANSWER a 1 × 10-3 M solution of NaCl a 1 × 10-4 M solution of HNO3 a solution with a pH of 3.0 If you would like to find the mass of a substance using a digital balance, but the balance reads 0.05 g before you add your sample, which of the following statements best describes what you should do? Select one: a. Put your sample on the balance and record the mass. The 0.05 g is small enough to be ignored. b. Put your sample on the balance, record the mass, then subtract 0.05 g. c. Put your sample on the balance, press the "tare" or "zero" button, and record the mass. d. Press the "tare" or "zero" button, wait for the balance to read 0.00, put your sample on the balance, and record the mass. ANSWER Predict the empirical formula of the ionic compound that forms from sodium and fluorine. Select one: a. Na2F3 b. NaF2 c. NaF ANSWER d. Na2F e. Na3F2 Which of the following would not neutralize a solution of H2SO4? Select one: a. ammonia b. lithium hydroxide c. nitric acid ANSWER d. sodium hydroxide When the following equation is balanced with the lowest whole number coefficients possible, what is the coefficient in front of Ca(OH)2? Ca(OH)2 + H3PO3 = H2O + Ca3(PO3)2 Select one: a. 1 b. 2 c. 3 ANSWER d. 6 An aqueous solution contains 0.100 M NaOH at 25.0°C. The pH of the solution is __________. Select one: a. 7.00 b. -1.00 c. 13.00 ANSWER d. 1.00 e. 0.100 An aliquot (28.7 mL) of a KOH solution required 31.3 mL of 0.118 M HCl for neutralization. What mass (g) of KOH was in the original sample? Select one: a. 1.64 b. 0.173 c. 0.207 ANSWER d. 7.28 e. 0.414 A 3.82-g sample of magnesium nitride is reacted with 7.73 g of water. Mg3N2 + 3H2O → 2NH3 + 3MgO The yield of MgO is 3.60 g. What is the percent yield in the reaction? Select one: a. 78.7 ANSWER b. 49.4 c. 94.5 d. 46.6 e. 99.9 A scientist in Germany published his findings from a scientific investigation that he conducted. Other scientists from around the world conducted similar investigations to test the results. All of the investigations result in similar findings. What does this say about the findings of these investigations? Select one: The findings are automatically promoted to a law because they were proven by so many scientists. They have been proven to be scientific fact because all the investigations gave similar findings. The results are considered more reliable because they were documented by separate investigations. ANSWER They are ready to be published in the media and in text books as a new scientific theory. A 0.03 mole sample of NH4NO3(s) is placed in a 1 L flask, which is then sealed and heated. The NH4NO3(s) decomposes completely according to the balanced equation below: NH4NO3(s) → N2O(g) + 2H2O(g) The total pressure in the flask measured at 400 K is closest to which of the following? 1 atm 3 atm ANSWER 0.5 atm 0.03 atm 0.1 atm An NaOH solution contains 1.90 mol of NaOH, and its concentration is 0.555 M. What is its volume? Select one: 0.911 L 3.42 L ANSWER 1.05 L 0.623 L Consider the mathematical expressions for gas laws listed, select the correct name for the law from the response list: P1V1 = P2V2. Select one: a. Avogadro's law b. Boyle's law ANSWER c. Charles's law d. combined gas law A wooden object has a mass of 10.782 g and occupies a volume of 13.72 mL. What is the density of the object? Select one: a. 0.815 g/mL b. 1.786 g/mL c. 1.272 g/mL d. 0.7859 g/mL ANSWER Which of the following compounds are soluble in water? Select one or more: a. zinc oxide b. potassium cyanide Correct. All Group 1A compounds are soluble. c. lead carbonate d. potassium perchlorate Correct! All Group 1A compounds and perchlorates are soluble.