Multiple choice questions

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Chapter 6: Structures and energetics of metallic and ionic solids

For some of these questions, you need data from the appendices of Inorganic Chemistry, third edition by C.E. Housecroft and A.G. Sharpe. On opening the book cover you will find a periodic table and a list of elements and atomic masses. Physical constants are listed on the back inside cover of the book.

Multiple choice questions by Catherine E. Housecroft.

This activity contains 20 questions.

Which statement is incorrect about a cubic close-packed lattice?

	All atoms have a coordination number of 12
	The lattice contains both tetrahedral and octahedral holes
	Layers of close-packed atoms are stacked in an ABABAB... pattern
	The packing is more efficient than in a body-centred cubic lattice

The coordination numbers of spheres in body-centred cubic, simple cubic and cubic close-packed lattices are, respectively:

	8, 6, 12
	6, 8, 12
	6, 12, 8
	8, 12, 12

Look at Table 6.2 in Inorganic Chemistry. Use the data to estimate the metallic radius of Ba in metallic barium at 298 K. The value (in pm) is:

	231
	217
	215
	197

Which statement is true?

	The electrical conductivity of a metal increases with temperature
	The electrical conductivity of a semiconductor increases with temperature
	The resistivity of a semiconductor increases with temperature
	Metals and semiconductors have similar electrical conducting properties

The behaviour of metals and semiconductors is usually discussed in terms of band theory. Which statement is not true?

	A partially filled band is characteristic of a metal
	Doping Si with As enhances its semiconducting properties
	Band gaps vary among different semiconductors but are always relatively large
	Band gaps for insulators are large

Which statement gives incorrect information about the formation of NaCl(s) from Na(s) and Cl₂(g)?

	Na is oxidized and Cl reduced
	An ionic structure forms
	Both the ionization of Na and electron attachment to Cl are exothermic processes
	When NaCl forms from its gaseous ions, energy is released

Which statement is true about an XY₂ lattice?

	The coordination number of X²ⁿ⁺ is twice that of Y^n–
	The coordination number of X²ⁿ⁺ is half that of Y^n–
	The unit cell contains twice as many X²ⁿ⁺ ions as Y^n–
	The coordination environments of X²ⁿ⁺ and Y^n– are the same

The standard enthalpy of formation of NaCl is –411 kJ mol^–1. Using data from the appendices of Inorganic Chemistry, calculate the value of Δ_latticeH^o(NaCl,s) (defined for the formation of NaCl). The value is:

	–1485 kJ mol^–1
	–787 kJ mol^–1
	+1485 kJ mol^–1
	+787 kJ mol^–1

Which of the following statements is incorrect?

	Madelung constants for MX₂ lattices are greater than those for MX lattices
	Use of the Born-Landé equation is restricted to lattices for which an electrostatic model is appropriate
	Madelung constants are structure dependent
	A lattice energy is an internal energy change, and Δ_latticeU(0 K) = Δ_latticeH(298 K)

Ions such as [CN]^– may be regarded as being spherical in some 3D-structures. This is because:

	each ion is approximately spherical
	the ions are freely rotating
	the ions are in random orientations
	the ions are either freely rotating or in random orientations

The coordination numbers of Ti(IV) and O^2– in rutile are, respectively:

	6 and 3
	3 and 6
	2 and 4
	4 and 2

An example of a compound that crystallizes with a layer structure is:

	CdI₂
	CaF₂
	ZnS
	SnO₂

Na₂S crystallizes with an antifluorite structure. Which statement is true about this structure?

	The coordination number of each S^2– centre is 8
	Each Na⁺ ion is within a cubic arrangement of S^2– ions
	The structure is based on an CaF₂ structure, with Na⁺ ions in Na₂S occupying the same sites as Ca²⁺ ions in CaF₂
	The S^2– ion is tetrahedrally sited

Which statement is incorrect?

	CaO crystallizes with the CsCl structure
	Wurtzite and zinc blende are polymorphs of ZnS
	β-Cristobalite is one crystalline form of SiO₂
	CaTiO₃ (perovskite) is an example of a double oxide

A unit cell of ReO₃ consists of a cubic arrangement of Re atoms with O atoms centred along each edge of the cube. The coordination number of each Re atom is:

	6
	3
	8
	2

Which of the following processes is exothermic?

	Na(s) → Na(g)
	Na(g) + e^- → Na^-(g)
	Na(g) → Na⁺(g) + e^-
	NaI(s) → Na⁺(g) + I^-(g)

Values of the Born exponents for Rb⁺ and I^- are 10 and 12, respectively. The Born exponent for RbI is therefore:

	11
	2
	22
	¹/₁₁

In solid NaCl, the coordination numbers of the Na⁺ and Cl^- ions are, respectively:

	6 and 6
	8 and 8
	12 and 12
	6 and 8

The electrical resistivity of titanium is 4.3 × 10^-7 Ω m. What is the resistance of a 0.50 m strip of titanium wire with cross section 8.0 × 10^-7 m²?

	3.7 Ω
	0.93 Ω
	0.27 Ω
	1.1 Ω

Arrange the following ions in order of decreasing size: Br^-, I^-, Mg²⁺, Ca²⁺

	I^- > Br^- > Ca²⁺ > Mg²⁺
	Br^- > I^- > Ca²⁺ > Mg²⁺
	Ca²⁺ > Mg²⁺ > I^- > Br^-
	I^- > Br^- > Mg²⁺ > Ca²⁺

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