Chapter 9 3 80 The Formal Charge The Sulfur Atom

Chapter 09 – Chemical Bonding I: Basic Concepts

80. The formal charge on the sulfur atom in the resonance structure of sulfur dioxide which

has one single bond and one double bond is

81. What is the formal charge on sulfur in the most favorable Lewis structure for the SCN–

(thiocyanate) ion based on minimizing formal charge overall?

Chapter 09 – Chemical Bonding I: Basic Concepts

82. What is the formal charge on the singly bonded oxygens in the Lewis structure for the

carbonate ion?

83. What is the formal charge on phosphorus in a Lewis structure for the phosphate ion that

satisfies the octet rule?

Chapter 09 – Chemical Bonding I: Basic Concepts

84. Nitrous oxide, N2O, is sometimes called “laughing gas”. What is the formal charge on the

central nitrogen atom in the most favorable Lewis structure for nitrous oxide based on

minimizing formal charge overall? (The atom connectivity is N–N–O.)

85. What is the formal charge on the central nitrogen atom in the most favorable Lewis

structure for the fulminate ion, CNO–, based on minimizing formal charge overall?

Chapter 09 – Chemical Bonding I: Basic Concepts

86. In the Lewis structure of the iodate ion, IO3–, that satisfies the octet rule, the formal charge

on the central iodine atom is

87. BeF42– is called the fluoberyllate ion. The formal charge on the beryllium atom in this ion

is

Chapter 09 – Chemical Bonding I: Basic Concepts

88. Each of the three resonance structures of NO3– has how many lone pairs of electrons?

89. For which of these species does the best Lewis structure have two or more equivalent

resonance structures?

Chapter 09 – Chemical Bonding I: Basic Concepts

90. What is the total number of lone pairs in the best Lewis structure for SOF4 that exceeds

the octet rule (S is the central atom)?

91. Which of the following substances will display an incomplete octet in its Lewis structure?

Chapter 09 – Chemical Bonding I: Basic Concepts

92. Which of the elements listed below is most likely to exhibit an expanded octet in its

compounds?

93. Which one of the following compounds does not follow the octet rule?

Chapter 09 – Chemical Bonding I: Basic Concepts

95. Which response includes all the molecules below that do not follow the octet rule?

(1) H2S (2) BCl3 (3) PH3 (4) SF4

Chapter 09 – Chemical Bonding I: Basic Concepts

96. Which one of the following molecules has an atom with an incomplete octet?

97. Which one of the following molecules has an atom with an expanded octet?

Chapter 09 – Chemical Bonding I: Basic Concepts

98. Which molecule has a Lewis structure that does not obey the octet rule?

99.

Estimate the enthalpy change for the reaction 2CO + O2→ 2CO2 given the following bond energies.

BE(CO) = 1074 kJ/mol

BE(O=O) = 499 kJ/mol

BE(C=O) = 802 kJ/mol

Chapter 09 – Chemical Bonding I: Basic Concepts

100.

Estimate the enthalpy change for the combustion of one mole of acetylene, C2H2, to form carbon dioxide and water vapor.

BE(C–H) = 456 kJ/mol

BE(CC) = 962 kJ/mol

BE(O=O) = 499 kJ/mol

BE(C=O) = 802 kJ/mol

BE(O–H) = 462 kJ/mol

101. Use bond energies to estimate the enthalpy of formation of HBr(g).

BE(H–H) = 436 kJ/mol

BE(Br–Br) = 192 kJ/mol

BE(H–Br) = 366 kJ/mol

Chapter 09 – Chemical Bonding I: Basic Concepts

102. Use bond energies to estimate the enthalpy change for the reaction of one mole of CH4

with chlorine gas to give CH3Cl and hydrogen chloride.

BE(C–H) = 414 kJ/mol

BE(C–Cl) = 326 kJ/mol

BE(H–Cl) = 432 kJ/mol

BE(Cl–Cl) = 243 kJ/mol

103.

Use the bond enthalpy data given to estimate the heat released when 6.50 g of nitrogen gas reacts with excess hydrogen gas

to form ammonia at 25C.

BE(NN) = 941.4 kJ/mol

BE(H–H) = 436.4 kJ/mol

BE(N–H) = 393 kJ/mol

Chapter 09 – Chemical Bonding I: Basic Concepts

104. Use the bond enthalpy data given to estimate the heat released when 50.0 g of propane

gas, C3H8, burns in excess oxygen to yield carbon dioxide and water vapor at 25C.

BE(C–C) = 347 kJ/mol

BE(C=O in CO2) = 799 kJ/mol

BE(C–H) = 414 kJ/mol

BE(O–H) = 460 kJ/mol

BE(O=O) = 498.7 kJ/mol

Chapter 09 – Chemical Bonding I: Basic Concepts

105.

Use the bond enthalpy data given to estimate the heat released when 25.0 g of acetylene gas, C2H2, burns in excess oxygen to

yield carbon dioxide and water vapor at 25C.

BE(C–C) = 347 kJ/mol

BE(CC) = 812 kJ/mol

BE(C=O in CO2) = 799 kJ/mol

BE(C–H) = 414 kJ/mol

BE(O–H) = 460 kJ/mol

BE(O=O) = 498.7 kJ/mol

106.

The standard enthalpy of formation of ammonia at 25C is –46.3 kJ/mol. Estimate the N–H bond enthalpy at this

temperature.

(Given: BE(NN) = 941.4 kJ/mol, BE(H–H) = 436.4 kJ/mol)

Chapter 09 – Chemical Bonding I: Basic Concepts

107.

Select True or False: The following Lewis dot symbol correctly depicts the chloride ion.

108.

Select True or False: The following correctly depicts the Lewis dot symbol for the sulfide ion.

Chapter 09 – Chemical Bonding I: Basic Concepts

109.

Calculate the energy required for the gas phase process represented by

Na(g) + Br(g) → Na+(g) + Br– (g).

Given:

Ionization energy (Na) = 496 kJ/mol

Electron affinity (Br) = 324 kJ/mol

Electron affinity (Na) = 53 kJ/mol

Chapter 09 – Chemical Bonding I: Basic Concepts

110.

Select True or False: The following reaction correctly shows the chemical equation for which the enthalpy of reaction is the

lattice energy of KCl(s).

KCl(s) → K+(g) + Cl – (g)

111.

Use the Born-Haber cycle to calculate the lattice energy of NaBr(s) given the following data:

H(sublimation) Na = 109 kJ/mol

I1 (Na) = 496 kJ/mol

Bond energy (Br–Br) = 192 kJ/mol

EA (Br) = 324 kJ/mol

Hf (NaBr(s)) = –361 kJ/mol

Chapter 09 – Chemical Bonding I: Basic Concepts

112. Select True or False: The compound Al(ClO3)3 shows only ionic bonding.

113. Select True or False: The molecule NH2NH2 shows both ionic and covalent bonding.

114. Select True or False: Covalent bonding is the only type of bonding present in the ClO2–

ion.