SmartBook Ch. 4 Pt. IV

True or false: An oxidation number is not the same as an actual charge on an ion.

True

Select all the reactions in which the oxidation numbers of the reactant species change, that is, are redox reactions. a) 7O2 (g) + 2C2H6 (l) → 4CO2 (g) + 6H2O (l) b) Co (s) + Cl2 (g) → CoCl2 (s) c) Cu(OH)2 (s) + 2HClO4 (aq) → Cu(ClO4)2 (aq) + H2O (l) d) ZnBr2 (aq) + 2KOH (aq) → Zn(OH)2 (s) + 2KBr (aq)

a) 7O2 (g) + 2C2H6 (l) → 4CO2 (g) + 6H2O (l) b) Co (s) + Cl2 (g) → CoCl2 (s)

Select all the reactions that are redox reactions. a) Ca(s) + 2H2O(l) → Ca2+(aq) + H2(g) + 2OH-(aq) b) NaCl(aq) + AgNO3(aq) → NaNO3(aq) + AgCl(s) c) H2SO3(aq) + H2O(l) → H3O+(aq) + HSO3-(aq) d) FeCl3(aq) + Al(s) → AlCl3(aq) + Fe(s)

a) Ca(s) + 2H2O(l) → Ca2+(aq) + H2(g) + 2OH-(aq) d) FeCl3(aq) + Al(s) → AlCl3(aq) + Fe(s)

Which of the following statements correctly describe a redox reaction? Select all that apply. a) Electrons always move from an atom that attracts them less strongly. b) This type of reaction involves the transfer of electrons. c) Redox reactions always involve charged species. d) Electrons always move toward an atom that is electron poor or electron deficient. e) Reduction and oxidation always occur together.

a) Electrons always move from an atom that attracts them less strongly. b) This type of reaction involves the transfer of electrons. e) Reduction and oxidation always occur together.

The equation 3Ni2+ (aq) + 2Cr (s) → 2Cr3+ (aq) + 3Ni (s) represents a redox reaction. In this reaction Ni2+ is the species _____ and is the _____ agent. a) reduced; oxidizing b) oxidized; oxidizing c) reduced; reducing d) oxidized; reducing

a) reduced; oxidizing

The redox process in the formation of covalent compounds from their elements involves a(n) _____ of electrons from the one element to the other. a) shift b) transfer c) net increase d) pairing

a) shift

The mass percent of alcohol (46.07 g/mol) in a 10. g sample of blood can be determined by titration with aqueous K2Cr2O7. The net ionic equation is given by: 2Cr2O72- (aq) + 3C2H5OH (aq) + 16H+ (aq) → 4Cr3+ (aq) + 3CH3COOH (g) + 11H2O (l). It requires 7.36 mL of 0.0177 M K2Cr2O7 solution to reach the endpoint. What is the mass percent of alcohol? (Legal intoxication is 0.080% in most states.) a) 0.0019% b) 0.090% c) 0.17% d) 0.35%

b) 0.090%

The reaction 2H2 (g) + O2 (g) → 2H2O (l) is a redox reaction although it does not involve any ionic species. How are electrons transferred in this type of reaction? a) H loses electrons to form an H+ cation that bonds with O. b) Electrons shift away from H toward O as the product is formed. c) Electrons "move" as nonpolar covalent bonds are replaced by polar covalent bonds. d) This is a proton transfer reaction.

b) Electrons shift away from H toward O as the product is formed. c) Electrons "move" as nonpolar covalent bonds are replaced by polar covalent bonds.

Select all the statements that correctly describe the following redox reaction, which is given as a molecular equation: Mg (s) + 2HCl (aq) → MgCl2 (aq) + H2 (g) a) Cl- is reduced to Cl22-. b) Mg is oxidized to Mg2+. c) H+ is the oxidizing agent. d) Mg2+ is the reducing agent. e) H+ is reduced to H2.

b) Mg is oxidized to Mg2+. c) H+ is the oxidizing agent. e) H+ is reduced to H2.

Which of the following statements correctly describe the rules for assigning oxidation numbers (abbreviated as O.N.)? Select all that apply. a) The sign of an oxidation number is unimportant. b) The O.N. for a monatomic ion is the same as its charge. c) If two atoms are bonded in a molecule, such as O2, the O.N. for one atom is +1 and for the other is -1 d) The sum of the oxidation numbers for the atoms in a neutral compound is zero. e) All elements in a covalent compound have an O.N. of zero.

b) The O.N. for a monatomic ion is the same as its charge. d) The sum of the oxidation numbers for the atoms in a neutral compound is zero.

Oxidation is defined as the _____ of electrons while reduction is the _____ of electrons. Multiple choice question. a) gain; loss b) loss; gain

b) loss; gain

At the equivalence point of a redox titration the number of electrons _____ by the oxidized species is _____ the number of electrons _____ by the reduced species. a) gained; less than; lost b) lost; equal to; gained c) lost; greater than; gained d) gained; equal to; lost

b) lost; equal to; gained

The oxidation of one species allows the reduction of another, so the species being oxidized is called the _____ agent while the species being reduced is the _____ agent. a) oxidizing; reducing b) reducing; oxidizing

b) reducing; oxidizing

Match each species to its correct oxidation number. 1) O in O2 2) Na in NaCl 3) O in H2O 4) Fe in FeCl3 a) -2 b) 0 c) +1 d) +3

b, c, a, d

In which of the following examples has the oxidation number (O.N.) of the given element been assigned correctly? Select all that apply. a) The O.N. for hydrogen in CuH is +1. b) The O.N. for Mn in KMnO4 is +2. c) The O.N. for chlorine in the ion ClO3- is +5. d) The O.N. for iron in FeO is +2. e) The O.N. for aluminum in Al2O3 is +2.

c) The O.N. for chlorine in the ion ClO3- is +5. d) The O.N. for iron in FeO is +2.

The concentration of Fe2+ in 15.00 mL of a water sample is determined by titration with aqueous KMnO4. The balanced net ionic equation is given by: MnO4- (aq) + 5Fe2+ (aq) + H+ (aq) → 5Fe3+ (aq) + Mn2+ (aq) + 4H2O (l) It requires 2.45 mL of 0.021 M KMnO4 solution to reach the endpoint, when the purple solution becomes colorless. Which of the following options correctly describe the analysis of the Fe2+ in the water sample? a) 0.051 moles of MnO4- are used in this titration. b) The concentration of Fe2+ is 6.8 × 10-4 M. c) There are 2.6 × 10-4 moles of Fe2+ in the water sample. d) There are 1.0 × 10-5 moles of Fe2+ in the water sample. e) The concentration of Fe2+ is 0.017 M.

c) There are 2.6 × 10-4 moles of Fe2+ in the water sample. e) The concentration of Fe2+ is 0.017 M.

An oxidation number is the _____ an atom would have if all bonds involved the _____ of electrons. The oxidation number can be used to track movement of electrons in chemical reactions. a) electrons; transfer b) bond number; sharing c) charge; transfer d) charge; sharing

c) charge; transfer

Oxidation, or the loss of electrons, will result in an element becoming _____ positive. This element will show a(n) _____ in oxidation number. Reduction, the gain of electrons, will cause an element to become _____ positive and the element will show a(n) _____ in oxidation number. a) more; decrease; less; increase b) less; decrease; more; increase c) more; increase; less; decrease d) less; increase; more; decrease

c) more; increase; less; decrease

Match each species involved in a redox reaction with its correct description. 1) The species oxidized shows a(n) 2) The species reduced shows a(n) 3) The species that shows a decrease in oxidation number is the 4) The species that shows an increase in oxidation number is the a) reducing agent. b) oxidizing agent. c) increase in oxidation number. d) decrease in oxidation number.

c, d, b, a

A redox titration may be used to determine the unknown concentration of a reducing agent by completing reacting it with a volume of a(n) _____ of known concentration. a) oxidation b) reducing agent c) reduction d) oxidizing agent

d) oxidizing agent

Match each element with its most common oxidation number (assuming it is involved in a polar/ionic bond). 1) -2 2) +1 3) -1 4) +2 a) H when bonded to other nonmetals b) Mg c) F d) O, in compounds other than peroxides

d, a, c, b

The movement of one or more_____ from one reactant to another is the key chemical event in an oxidation - _____ reaction, also called a(n) _____ reaction.

electrons, reduction, redox

In redox titrations, the equivalence point occurs when the electrons lost by the _____ species equal the electrons gained by the _____ species.

oxidized, reducing