147 Created by Master Student Chemistry Practice Test #7 1 / 30 A student conducted an experiment and obtained three values during three repetitive trials: 1.65, 1.68, 1.71. Later, the student discovered that the true value was 2.37. In contrast to the real value, the experimental results should be characterized as not accurate and not precise accurate but not precise not accurate but precise accurate and precise accurate, precise, but unreliable By definition, accuracy is the measure of how close experimental data are to true data, while precision is the measure of how similar experimental data are to one another. Clearly, the student's data is very precise; the values of 1.65, 1.68, 1.71 vary by no more than 4 percent. However, the average value of the experimental data is nearly 50 percent off the true value, meaning these results are not very accurate-choice (C). 2 / 30 What is the number of protons and neutrons in an atom with mass number 89 and atomic number 39? 50 protons and 50 neutrons 50 protons and 39 neutrons 39 protons and 89 neutrons 39 protons and 50 neutrons 39 protons and 39 neutrons The atomic number is the number of protons in the nucleus, and the mass number is the sum: number of protons + number of neutrons. If the atomic number is 39 and the mass number is 89, then the number of neutrons in the nucleus must be (89) - (39) = 50. 3 / 30 If the sharing of an electron pair is unequal and the atoms have an electronegativity difference of 1.4 to 1.6, what is this type of sharing called? ionic covalent polar covalent metallic hydrogen bonding (C) When the electronegativity difference between the two bonding atoms is between 0.3 and 1.7, the electrons are not equally shared and result in a polar covalent bond. 4 / 30 Is the third most abundant gas in Earth's atmosphere Carbon Nitrogen Oxygen Neon Argon The composition of Earth's atmosphere is approximately 78% N2, 20% O2, 1% Ar, 0.5% H2O, 0.4% CO2, and 0.1% other trace gases. 5 / 30 What piece of apparatus can be used to introduce more liquid into a reaction and also serve as a pressure valve? Stopcock Pinchcock Thistle tube Flask Condenser (C) The thistle tube serves both these purposes. 6 / 30 The normal configuration for ethyne (acetylene) is H-CC-H H-C-C-H H-CH2-CH2-H H-CC-H H-CH-CH-H (D) The ethyne molecule is the first member of the acetylene series with a general formula of CnH2n-2. It contains a triple bond between the two C atoms: H-CC-H. 7 / 30 An ester can be prepared by the reaction of two alcohols an alcohol and an aldehyde an alcohol and an organic acid an organic acid and an aldehyde an acid and a ketone (C) The formation of an ester is from the reaction of an organic acid and an alcohol. The general equation is: 8 / 30 For the radioactive atom 99Tc, what is the correct number of protons and neutrons? 43 protons and 56 neutrons 43 protons and 99 neutrons 56 protons and 43 neutrons 56 protons and 99 neutrons Cannot be determined After examining the periodic table, realize that the full atomic symbol for this isotope of technicium is 9 / 30 A liquid will boil when its freezing point is equal to its melting point a salt has been added to the liquid its vapor pressure is equal to the melting point it is heated to a temperature that is below the boiling point its vapor pressure is equal to the surrounding pressure 0 10 / 30 This is the minimum energy needed for molecules to react and form compounds. Reduction potential Ionization energy Electronegativity Heat of formation Activation energy (E) The activation energy is defined as the minimum energy required for molecules to react . This is true for both exothermic and endothermic reactions. 11 / 30 At a particular temperature and pressure, three states of a substance may coexist. Law of Definite Composition Nuclear fusion van der Waals forces Graham's Law of Diffusion (Effusion) Triple point (E) A phase diagram shows that all three states can exist at the triple point. 12 / 30 Compounds that have the same composition but differ in their structural formulas are used for substitution products are called isomers are called polymers have the same properties are usually alkanes (B) Isomers are compounds that have the same composition but differ in their structural formulas. 13 / 30 Identify the equation used to determine the amount of heat required to melt 10 grams of ice. Q = mCspΔT Q = nΔH KE = mv2 PE = mgh PV = nRT First, the correct abbreviation for heat is Q. So we can eliminate choices (C), (D), and (E). During a phase change, the temperature of a substance remains constant. Therefore, choice (A) must be wrong because it has a term for changing temperature, ΔT. In fact, choice (A) is the equation used to determine the change in temperature when heat is added or removed from a substance that isn't undergoing a phase change. Choice (B) is the correct choice, where Q is the heat added or removed, n is the number of moles of substance, and ΔH is the heat of phase change, a quantity that is unique for every substance. 14 / 30 Which of the following statements is NOT correct regarding chemical catalysts? They are not consumed during the chemical reaction. They cannot make nonspontaneous reactions occur. They do not have to be the same phase as the reactant molecules. They shift equilibrated reactions to the product's side. Enzymes are biological catalysts. The addition of a catalyst to a system at equilibrium has NO effect. That's because all a catalyst does is increase the rate at which a nonequilibrated system reaches equilibrium. 15 / 30 Which solution listed below is going to have the highest boiling point? 1.5 m NaCl 1.5 m AgCl 2.0 m C6H12O6 2.0 m CaCl2 1.0 m Al2(SO4)3 0 16 / 30 Which gas under a high temperature and a low pressure behaves most like an ideal gas? He O2 NH3 CO2 Ne 0 17 / 30 Which of the following is not a conclusion Rutherford made from his experiment with alpha particles being shot at a thin sheet of gold foil? An atom has a very small, compact nucleus. An atom is mainly empty space. An atom's mass is concentrated in the nucleus. An atom has a very dense nucleus. An atom has a negatively charged nucleus. 0 18 / 30 A mixture of gases exists in a sealed container with the following percentages: helium 40%, neon 50%, and argon 10%.If the total pressure of the gases is 1100 torr, then which of the following is true about these gases? Volume and temperature have an inversely proportional relationship. Volume and pressure have a direct relationship. The partial pressure of the neon gas is 550 torr. The partial pressure of the argon gas is 100 torr. The partial pressures of the gases cannot be calculated with the given information. 0 19 / 30 Which atom is not paired with its correction and ionic charge? Rb / Rb1- Mg / Mg2+ F / F1- Li / Li1+ Br / Br1- 0 20 / 30 Members possess the lowest first ionization energy in their respective period Alkali metals Alkaline earth metals Noble gases Halogens Transition metals Ionization energy is needed to remove an electron from an atom. Which kind of elements tend to give up electrons? Metals, of course. Of the metals, alkali metals, having only 1 valence electron per atom, will lose an electron most easily because this allows an alkali metal atom to assume a stable noble gas electron configuration. 21 / 30 Laboratory results showed the composition of a compound to be 58.81% barium, 13.73% sulfur, and 27.46% oxygen. What is the empirical formula of the compound? BaSO4 BaS2O Ba2SO3 BaS2O4 Ba2SO4 (A) Dividing the percentage of each element by the atomic mass of that element gives the basic ratio of atoms, but not necessarily in whole numbers. Thus, (Ba) 58.8 ÷ 137 = 0.43, (S) 13.7 ÷ 32 = 0.43, (O) 27.5 ÷ 16 = 1.72. 22 / 30 Which substance has a polar covalent bond between its atoms? K3N Ca3N2 NaCl F2 NH3 0 23 / 30 An oxidation-reduction reaction takes place in a chemical cell, and the flow of electrons is used to provide energy for a lightbulb. Which of the following statements is true of the reaction? The reaction is nonspontaneous and has a positive voltage. The reaction is nonspontaneous and has a negative voltage. The reaction is at equilibrium and has a voltage of zero. The reaction is spontaneous and has a positive voltage. The reaction is spontaneous and has a negative voltage. If the reaction is being used to provide energy to electrons, it must have a positive reaction potential or voltage. In the same way, if the reaction is being used to provide energy to a circuit, it must be spontaneous (?G is negative). 24 / 30 What volume of 0.4 M Ba(OH)2 (aq) is needed to exactly neutralize 100 milliliters of 0.2 M HBr(aq)? 25 mL 50 mL 100 mL 200 mL 400 mL First consider the neutralization that occurs between HBr and Ba(OH)2. 25 / 30 Which of the following statements is true? NaCl is a neutral salt. KC2H3O2 is an acidic salt. KOH is an acid. HCl and KOH react to form hydrogen gas and water. NaBr is basic salt. 0 26 / 30 Proposes a relationship between the combining volumes of gases with respect to the reactants and gaseous products Avogadro's number P1V1 = P2V2 V1T2 = V2T1 Dalton's Theory Gay-Lussac's Law (E) Gay-Lussac is credited with the statement that, when gases combine, they do so in ratios of small whole numbers that are in relationship to the volumes of the reactants and the volumes of the products under the same conditions. 27 / 30 A molecule in which the electron configuration is a resonance hybrid is SO2 C2H6 Cl2 HBr NaCl (A) The structure of SO2 is a resonance hybrid, shown as these resonance structures: 28 / 30 The expression that can be used to designate 2 moles of atoms H2(g) CO2(g) 2N2O(g) 2NaCl (aq) H2SO4(dilute aq) (A) A hydrogen gas molecule is diatomic; it has 2 mol of atoms in each mole of molecules, represented by H2. 29 / 30 Which of the following gases is expected to have the lowest density at STP? SO2 CO2 Cl2 Xe Ar 0 30 / 30 Making reference to electronegativity values, which substance is most easily reduced? Br2 Cl2 F2 I2 At2 0 Your score is The average score is 55% LinkedIn Facebook Twitter VKontakte 0% Restart quiz Previous Quiz Next Quiz
