Questions and Answers of Chemistry The Central Science

The lanthanide contraction explains which of the following periodic trends?(a) The atomic radii of the transition metals first decrease and then increase when moving horizontally across each
The three graphs below show the variation in radius, effective nuclear charge, and maximum oxidation state for the transition metals of period 4. In each part below identify which property is being
Using ΔG°f for ozone from Appendix C, calculate the equilibrium constant for Equation 22.24 at 298.0 K, assuming no electrical input. electricity 3 02(g) 2 03(g) AH° 285 k %3D
Determine the charge of the aluminosilicate ion whose composition is AlSi3O10.
Indicate whether each of the following statements is true or false(a) H2 (g) and D2 (g) are allotropic forms of hydrogen.(b) ClF3 is an interhalogen compound.(c) MgO (s) is an acidic anhydride.(d)
(a) Determine the number of sodium ions in the chemical formula of albite, NaxAlSi3O8.(b) Determine the number of hydroxide ions in the chemical formula of tremolite, Ca2Mg5(Si4O11)2(OH)x.
(a) Determine the number of calcium ions in the chemical formula of the mineral hdystonite, CaxZn(Si2O7).(b) Determine the number of hydroxide ions in the chemical formula of the mineral
Explain the following observations:(a) For a given oxidation state, the acid strength of the oxyacid in aqueous solution decreases in the order chlorine > bromine > iodine.(b) Hydrofluoric acid
Explain each of the following observations:(a) At room temperature I2 is a solid, Br2 is a liquid, and Cl2 and F2 are both gases(b) F2 cannot be prepared by electrolytic oxidation of aqueous F
Naturally found uranium consists of 99.274% 238U, 0.720% 235U, and 0.006% 233U. As we have seen, 235U is the isotope that can undergo a nuclear chain reaction. Most of the 235U used in the first
Each of the following transmutations produces a radionuclide used in positron emission tomography (PET).(a) In equations (i) and (ii), identify the species signified as “X.”(b) In equation (iii),
In 2010, a team of scientists from Russia and the U.S. reported creation of the first atom of element 117, which is not yet named and is denoted [117]. The synthesis involved the collision of a
The table to the right gives the number of protons (p) and neutrons (n) for four isotopes.(a) Write the symbol for each of the isotopes.(b) Which of the isotopes is most likely to be unstable?(c)
Complete and balance the nuclear equations for the following fission or fusion reactions:(a) 21H + 21H → 32He + __(b) 23992U + 10n → 13351Sb + 9841Nb + __ 10n
Which of the following statements about the uranium used in nuclear reactors is or are true?(i) Natural uranium has too little 235U to be used as a fuel.(ii) 238U cannot be used as a fuel because it
(a) Which of the following are required characteristics of an isotope to be used as a fuel in a nuclear power reactor? (i) It must emit gamma radiation. (ii) On decay, it must release two or more
It takes 4 h 39 min for a 2.00-mg sample of radium-230 to decay to 0.25 mg. What is the half-life of radium-230?
Complete and balance the following nuclear equations by supplying the missing particle:(a) 147N + 42He → ? + 11H(b) 4019K + 0-1e (orbital electron) → ?(c) ? + 42He → 3014Si + 11H(d) 5826Fe +
Which of the following nuclides would you expect to be radioactive: 5826Fe, 6027Co, 9241Nb, Mercury-202, Radium-226 ? Justify your choices.
Indicate the number of protons and neutrons in the following nuclei:(a) 12953I(b) 138Ba(c) Neptunium-237
Indicate the number of protons and neutrons in the following nuclei:(a) 5624Cr(b) 193Tl(c) Argon-38.
The accompanying graph illustrates the decay of 8842Mo, which decays via positron emission.(a) What is the half-life of the decay?(b) What is the rate constant for the decay?(c) What fraction of the
The steps below show three of the steps in the radioactive decay chain for 23290Th. The half-life of each isotope is shown below the symbol of the isotope.(a) Identify the type of radioactive decay
In the sketch below, the red spheres represent protons and the gray spheres represent neutrons.(a) What are the identities of the four particles involved in the reaction depicted?(b) Write the
Magnesium is obtained by electrolysis of molten MgCl2.(a) Why is an aqueous solution of MgCl2 not used in the electrolysis?(b) Several cells are connected in parallel by very large copper bars that
A common shorthand way to represent a voltaic cell is anode| anode solution || cathode solution |cathode A double vertical line represents a salt bridge or a porous barrier. A single vertical line
Li-ion batteries used in automobiles typically use a LiMn2O4 cathode in place of the LiCoO2 cathode found in most Li-ionbatteries.(a) Calculate the mass percent lithium in each electrode material?(b)
In a Li-ion battery the composition of the cathode is LiCoO2 when completely discharged. On charging approximately 50% of the Li+ ions can be extracted from the cathode and transported to the
In some applications nickel–cadmium batteries have been replaced by nickel–zinc batteries. The overall cell reaction for this relatively new battery is:2H2O(I) + 2NiO(OH)(s) + Zn(s) →
(a) In the Nernst equation what is the numerical value of the reaction quotient, Q, under standard conditions?(b) Can the Nernst equation be used at temperatures other than room temperature?
Based on the data in Appendix E(a) which of the following is the strongest oxidizing agent and which is the weakest in acidic solution: Br2, H2O2, Zn, Cr2O72- ?(b) Which of the following is the
From each of the following pairs of substances, use data in Appendix E to choose the one that is the stronger reducing agent:(a) Fe(s) or Mg(s)(b) Ca(s) or Al(s)(c) H2(g, acidic solution) or
(a) What is the standard reduction potential of a standard hydrogen electrode?(b) Why is it impossible to measure the standard reduction potential of a single half-reaction?
Complete and balance the following equations, and identify the oxidizing and reducing agents:(a) Cr2O72-(aq) + I-(aq) → Cr3+(aq) + IO3- (aq) (acidic solution)(b) MnO4- (aq) + CH3OH(aq)
Complete and balance the following half-reactions. In each case indicate whether the half-reaction is an oxidation or a reduction.(a) Mo3+ (aq) → Mo(s) (acidic solution)(b) H2SO3 (aq) →
Complete and balance the following half-reactions. In each case indicate whether the half-reaction is an oxidation or a reduction.(a) Sn2+(aq) → Sn4+(aq) (acidic solution)(b) TiO2(s) → Ti2+(aq)
Indicate whether the following balanced equations involve oxidation–reduction. If they do, identify the elements that undergo changes in oxidation number.(a) 2AgNO3(aq) + CoCl2(aq) → 2AgCl(s) +
In each of the following balanced oxidation–reduction equations, identify those elements that undergo changes in oxidation number and indicate the magnitude of the change in each case.2MnO4-(aq) +
Bars of iron are put into each of the three beakers as shown here. In which beaker—A, B, or C—would you expect the iron to show the most corrosion? Beaker A Pure water Beaker B Dilute HCI (aq)
The electrodes in a silver oxide battery are silver oxide (Ag2O) and zinc. Which electrode acts as the anode?
An ice cube with a mass of 20g at -20°C (typical freezer temperature) is dropped into a cup that holds 500 mL of hot water, initially at 83°C. What is the final temperature in the cup? The density
At what temperatures is the following reaction, the reduction of magnetite by graphite to elemental iron, spontaneous?Fe3O4(s) + 2C (s, graphite) → 2CO2(g) + 3 Fe(s)
Indicate whether ΔG increases, decreases, or stays the same for each of the following reactions as the partial pressure of O2 is increased:(a) 2CO(g) + O2(g) → 2CO2(g)(b) 2H2O2(I) → 2H2O(I) +
Indicate whether each statement is true or false.(a) Unlike enthalpy, where we can only ever know changes in H, we can know absolute values of S.(b) If you heat a gas such as CO2, you will increase
Indicate whether each statement is true or false.(a) The third law of thermodynamics says that the entropy of a perfect, pure crystal at absolute zero increases with the mass of the crystal.(b)
Does the entropy of the system increase, decrease, or stay the same when(a) The temperature of the system increases.(b) The volume of a gas increases.(c) Equal volumes of ethanol and water are mixed
Indicate whether each statement is true or false.(a) ΔS for an isothermal process depends on both the temperature and the amount of heat reversibly transferred.(b) ΔS is a state function.(c) The
Indicate whether each statement is true or false. All spontaneous processes are irreversible?
Indicate whether each statement is true or false.(a) If a system undergoes a reversible process, the entropy of the universe increases.(b) If a system undergoes a reversible process, the change in
(a) Can endothermic chemical reactions be spontaneous?(b) Can a process that is spontaneous at one temperature be nonspontaneous at a different temperature?
The Henry’s law constant for CO2 in water at 25°C is 3.1 × 10-2M atm-1.What is the solubility of CO2 in water at this temperature if the solution is in contact with air at normal atmospheric
It was estimated that the eruption of the Mount Pinatubo volcano resulted in the injection of 20 million metric tons of SO2 into the atmosphere. Most of this SO2 underwent oxidation to SO3, which
(a) Suppose that tests of a municipal water system reveal the presence of bromate ion, BrO3-. What are the likely origins of this ion?(b) Is bromate ion an oxidizing or reducing agent? Write a
In the lime soda process at one time used in large scale municipal water softening, calcium hydroxide prepared from lime and sodium carbonate are added to precipitate Ca2+ as CaCO3(s) and Mg2+ as
The Ogallala aquifer described in the Closer Look box in Section 18.3, provides 82% of the drinking water for the people who live in the region, although more than 75% of the water that is pumped
Which of the following reactions in the stratosphere cause an increase in temperature there?(a) O(g) + O2(g) ⇌ O3* (g)(b) O3* (g) + M(g) ⇌ O3(g) + M* (g)(c) O2(g) + hν ⇌
From study of Figure 18.22 describe the various ways in which operation of a fracking well site could lead to environmental contamination. Waste water ponds Fracking fluid Contaminants escape to
Where does the energy come from to evaporate the estimated 425,000 km3 of water that annually leaves the oceans, as illustrated here? Water transport to the atmosphere Earth's atmosphere World осean
Oxalic acid (H2C2O4) is a diprotic acid. By using data in Appendix D as needed, determine whether each of the following statements is true:(a) H2C2O4 can serve as both a Brønsted– Lowry acid and a
(a) If Qc < Kc, in which direction will a reaction proceed in order to reach equilibrium? (b) What condition must be satisfied so that Qc = Kc?(b) What condition must be satisfied so that Qc = Kc?
(a) If Qc > Kc, how must the reaction proceed to reach equilibrium?(b) At the start of a certain reaction, only reactants are present; no products have been formed. What is the value of Qc at this
At 100 °C, the equilibrium constant for the reactionCOCl2(g) ⇌ CO(g) + Cl2(g) has the value Kc = 2.19 × 10-10.Are the following mixtures of COCl2, CO, and Cl2 at 100°C at equilibrium? If not,
For the reaction H2(g) + I2(g) ⇌ 2HI(g), Kc = 55.3 at 700 K. In a 2.00-L flask containing an equilibrium mixture of the three gases, there are 0.056 g H2 and 4.36 g I2. What is the mass of HI in
For 2SO2(g) + O2(g) ⇌ 2SO3(g), Kp = 3.0 × 104 at 700 K. In a 2.00-L vessel, the equilibrium mixture contains 1.17 g of SO3 and 0.105 g of O2. How many grams of SO2 are in the vessel?
Consider the reactionCaSO4(s) ⇌ Ca2+(aq) + SO42-(aq)At 25°C, the equilibrium constant is Kc = 2.4 × 10-5 for this reaction.(a) If excess CaSO4(s) is mixed with water at 25°C to produce a
At 25°C, the reaction CaCrO4(s) ⇌ Ca2+(aq) + CrO42-(aq) has an equilibrium constant Kc = 7.1 × 10-4. What are the equilibrium concentrations of Ca2+ and CrO42- in a saturated solution of CaCrO4?
Consider the reaction4NH3(g) + 5O2(g) ⇌ 4NO(g) + 6H2O(g), ΔH = -904.4 kJDoes each of the following increase, decrease, or leave unchanged the yield of NO at equilibrium?(a) Increase [NH3](b)
The water–gas shift reactionCO(g) + H2O(g) ⇌ CO2(g) + H2(g) is used industrially to produce hydrogen.The reaction enthalpy is ΔH° = -41 kJ.(a) To increase the equilibrium yield of hydrogen
Consider the hypothetical reaction A(g) ⇌ 2 B(g). A flask is charged with 0.75 atm of pure A, after which it is allowed to reach equilibrium at 0°C. At equilibrium, the partial pressure of A is
As shown in Table 15.2, the equilibrium constant for the reaction N2(g) + 3H2(g) ⇌ 2 NH3(g) is Kp = 4.34 × 10-3 at 300°C. Pure NH3 is placed in a 1.00-L flask and allowed to reach equilibrium at
For the equilibriumPH3BCl3(s) ⇌ PH3(g) + BCl3(g) Kp = 0.052 at 60 °C.(a) Calculate Kc.(b) After 3.00 g of solid PH3BCl3 is added to a closed 1.500-L vessel at 60°C, the vessel is charged with
Consider the hypothetical reaction A(g) + 2B(g) ⇌ 2C(g), for which Kc = 0.25 at a certain temperature. A 1.00-L reaction vessel is loaded with 1.00 mol of compound C, which is allowed to reach
Silver chloride, AgCl(s), is an “insoluble” strong electrolyte.(a) Write the equation for the dissolution of AgCl(s) in H2O(I).(b) Write the expression for Kc for the reaction in part (a).(c)
The probe of the pH meter shown here is sitting in a beaker that contains a clear liquid. (a) You are told the liquid is pure water, a solution of HCl(aq), or a solution of KOH(aq). Which one is
The graph given below shows [H+] vs. concentration for an aqueous solution of an unknown substance.(a) Is the substance a strong acid, a weak acid, a strong base, or a weak base?(b) Based on your
Phenylephrine, an organic substance with molecular formula C9H13NO2, is used as a nasal decongenstant in over-thecounter medications. The molecular structure of phenylephrine is shown below using the
If a neutral solution of water, with pH = 7.00, is cooled to 10°C, the pH rises to 7.27. Which of the following three statements is correct for the cooled water:(i) [H+] > [OH-](ii) [H+] =
Addition of the indicator methyl orange to an unknown solution leads to a yellow color. The addition of bromthymol blue to the same solution also leads to a yellow color.(a) Is the solution acidic,
Addition of phenolphthalein to an unknown colorless solution does not cause a color change. The addition of bromthymol blue to the same solution leads to a yellow color.(a) Is the solution acidic,
Is each of the following statements true or false?(a) All strong acids contain one or more H atoms.(b) A strong acid is a strong electrolyte.(c) A 1.0-M solution of a strong acid will have pH = 1.0.
Determine whether each of the following is true or false:(a) All strong bases are salts of the hydroxide ion. (b) The addition of a strong base to water produces a solution of pH >
Calculate [OH-] and pH for(a) 1.5 × 10-3M Sr(OH)2(b) 2.250 g of LiOH in 250.0 mL of solution(c) 1.00 mL of 0.175 M NaOH diluted to 2.00 L(d) A solution formed by adding 5.00 mL of 0.105 M KOH to
A solution of sodium acetate (NaCH3COO) has a pH of 9.70. What is the molarity of the solution?
Pyridinium bromide (C5H5NHBr) is a strong electrolyte that dissociates completely into C5H5NH+ and Br-. A solution of pyridinium bromide has a pH of 2.95. What is the molarity of the solution?
Benzoic acid (C6H5COOH) and aniline (C6H5NH2) are both derivatives of benzene. Benzoic acid is an acid with Ka = 6.3 × 10-5 and aniline is a base with Ka = 4.3 × 10-10.(a) What are the conjugate
The equilibrium 2NO(g) + Cl2(g) ⇌ 2NOCl(g) is established at 500K. An equilibrium mixture of the three gases has partial pressures of 0.095 atm, 0.171 atm, and 0.28 atm for NO, Cl2, and
Repeat Exercise 12.47 for a linear chain of eight lithium atoms.Data from Repeat exercise 12.47The molecular-orbital diagrams for two- and four-atom linear chains of lithium atoms are shown in Figure
Determine if each statement is true or false:(a) Substitutional alloys are solid solutions, but interstitial alloys are heterogenous alloys.(b) Substitutional alloys have “solute” atoms that
Which of these molecular fragments would you expect to be more likely to give rise to electrical conductivity? Explain your reasoning.a.b.
Two solids are shown below. One is a semiconductor and one is an insulator. Which one is which? Explain your reasoning.
Which arrangement of cations (yellow) and anions (blue) in a lattice is the more stable? Explain your reasoning. (a) (b)
The electronic structure of a doped semiconductor is shown here.(a) Which band, A or B, is the valence band?(b) Which band is the conduction band?(c) Which band consists of bonding molecular
You are given a white substance that sublimes at 3000°C; the solid is a nonconductor of electricity and is insoluble in water. Which type of solid (molecular, metallic, covalent-network, or ionic)
Imagine the primitive cubic lattice. Now imagine grabbing the top of it and stretching it straight up. All angles remain 90°. What kind of primitive lattice have you made?
Imagine the primitive cubic lattice. Now imagine pushing on top of it, straight down. All angles remain 90°. What kind of primitive lattice have you made?
Which of the three-dimensional primitive lattices has a unit cell where none of the internal angles is 90°?(a) Orthorhombic(b) Hexagonal(c) Rhombohedral(d) Triclinic(e) Both rhombohedral and
Besides the cubic unit cell, which other unit cell(s) has edge lengths that are all equal to each other?(a) Orthorhombic(b) Hexagonal(c) Rhombohedral(d) Triclinic(e) Both rhombohedral and triclinic.
For each of these solids, state whether you would expect it to possess metallic properties:(a) TiCl4(b) NiCo alloy(c) W(d) Ge(e) ScN.
Which of these statements about alloys and intermetallic compounds is false?(a) Bronze is an example of an alloy.(b) “Alloy” is just another word for “a chemical compound of fixed composition
State whether each sentence is true or false:(a) Metals have high electrical conductivities because the electrons in the metal are delocalized.(b) Metals have high electrical conductivities because

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