Question 1

How many atoms are in one face-centered cubic unit cell of a metal?

Accepted Answer

There are 4 atoms in one face-centered cubic unit cell of a metal. This is because each of the 8 corner atoms contributes 1/8 of its volume to the unit cell, and each of the 6 face-centered atoms contributes 1/2 of its volume to the unit cell. Therefore, the total number of atoms in a face-centered cubic unit cell is 4 (1 + 6 x 1/2 + 8 x 1/8 = 4).

Question 2

Which is classified as an amorphous solid?

Accepted Answer

Amorphous solids are materials that lack the long-range ordered structure of crystals. Plastic is an example of an amorphous solid, while palladium(II)chloride, phosphorus tetrachloride, and platinum are crystalline solids.

Question 3

Hydroquinone is an antioxidant that is also used as a photographic reducer and developer.The normal boiling point of hydroquinone is 310°C.Calculate the pressure at which hydroquinone will boil at 200°C given that its ΔH_vap is 73.38 kJ/mol.

Accepted Answer

First, we need to use the Clausius-Clapeyron equation:

ln (P2/P1) = ΔHvap/R ((1/T1) - (1/T2))

where P1 and T1 are the known boiling point and its corresponding pressure (1 atm), P2 is the pressure we want to find, T2 is the given boiling point (200°C + 273.15 = 473.15 K), ΔHvap is the enthalpy of vaporization, and R is the gas constant (8.314 J/mol*K).

We convert the given ΔHvap from kJ/mol to J/mol:

ΔHvap = 73.38 * 1000 J/mol = 73,380 J/mol

Rearranging the equation with the known values and solving for P2:

ln (P2/1 atm) = (73,380 J/mol)/(8.314 J/mol*K) ((1/310 K) - (1/473.15 K))

ln (P2/1 atm) = -18.357

P2/1 atm = e^(-18.357)

P2 = 2.25 x 10^-8 atm

Converting to mm Hg:

P2 = 2.25 x 10^-8 atm x 760 mm Hg/atm = 1.71 x 10^-5 mm Hg

Therefore, the closest choice is C: 22.5 mm Hg.

Question 4

Which type of bonding does Mg form upon solidification?

Accepted Answer

Magnesium (Mg) forms metallic bonds upon solidification, as it is a metal and its atoms share a "sea of electrons" that allows them to conduct electricity and heat.

Question 5

Which of the following forms a molecular solid?

Accepted Answer

C₁₀H₂₂ is a molecular solid known as sucrose (table sugar). CaO is an ionic solid, C(graphite) is a covalent network solid, and gold is a metallic solid.

Question 6

Which of the following statements is not consistent with the properties of a molecular solid?

Accepted Answer

Molecular solids are made up of molecules held together by intermolecular forces, and do not conduct electricity when solid. The presence of conductivity when molten indicates that the compound is likely an ionic compound, which would not be considered a molecular solid.

Question 7

While mercury is very useful in barometers,mercury vapor is toxic.Given that mercury has a ΔH_vap of 59.11 kJ/mol and its normal boiling point is 356.7°C,calculate the vapor pressure in mm Hg at room temperature,25°C.

Accepted Answer

To calculate the vapor pressure of mercury at 25°C, we need to use the Clausius-Clapeyron equation:

ln(P2/P1) = (-ΔHvap/R) * (1/T2 - 1/T1)

where P1 is the vapor pressure at the normal boiling point (356.7°C), P2 is the vapor pressure at 25°C, ΔHvap is the enthalpy of vaporization, R is the gas constant, and T1 and T2 are the temperatures in Kelvin.

Converting the boiling point to Kelvin, we get:

T1 = 356.7 + 273.15 = 629.85 K
T2 = 25 + 273.15 = 298.15 K

Substituting the values into the equation and solving for P2, we get:

P2 = P1 * e^((-ΔHvap/R) * (1/T2 - 1/T1))

Using the given values for ΔHvap and the gas constant (R = 8.314 J/mol·K), we get:

P2 = P1 * e^((-59110 J/mol) / (8.314 J/mol·K * 298.15 K) * (1/298.15 K - 1/629.85 K))

Converting from J to kJ and from kPa to mm Hg (1 kPa = 7.50062 mm Hg), we get:

P2 = 101.325 kPa * e^(-1.988) = 0.0002668 kPa = 2.68 × 10^-3 mm Hg

Therefore, the vapor pressure of mercury at 25°C is 2.68 × 10^-3 mm Hg, which is closest to answer choice A).

Question 8

The wavelength of light used to observe an object must be ________ than the object itself.

Accepted Answer

The wavelength of light used to observe an object must be smaller than the object itself. This is because the wavelength of light determines the level of detail we can see in an image. If the wavelength is too large, it will not be able to resolve smaller features of the object. Therefore, we need a smaller wavelength to see smaller details.

Question 9

Which of the following forms an ionic solid?

Accepted Answer

RbI is the only choice that pairs a cation (Rb+) with an anion (I-) to form an ionic solid. The other choices are either pure elements (Ag, S) or molecular compounds (C₇H₁₅NH₂, SO₃) that do not form ionic solids.

Question 10

A crystalline solid of unknown origin forms an aqueous solution that conducts an electrical current.The solid has a high melting point and shatters when struck with a hammer.The solid is likely to be

Accepted Answer

The fact that the solid forms an aqueous solution that conducts an electrical current suggests that ions are present, which would be the case for an ionic solid. The high melting point and brittleness are also consistent with ionic solids. Covalent network solids and metallic solids generally do not dissolve in water and do not conduct electricity as liquids or solutions. Molecular solids may dissolve in water but do not conduct electricity unless they are ionized.

Question 11

A kitchen pressure cooker operates at 1.50 atm.The ΔH_vap of water is 40.7 kJ/mol.What is the boiling point of water in the pressure cooker?

Accepted Answer

The answer of A kitchen pressure cooker operates at 1.50...

Question 12

Which of the following compounds forms a covalent network solid?

Accepted Answer

Covalent network solids are characterized by a network of covalent bonds, resulting in a very large macromolecule or lattice structure. The compound that fits this description is SiO2 (silicon dioxide), represented by choice C. The other compounds are not covalent network solids. Choice A seems to be a made-up compound, and choices B and D are molecular compounds with relatively low melting/boiling points.

Question 13

The structure of a solid can be determined by diffraction of radiation in which region of the electromagnetic radiation spectrum?

Accepted Answer

The diffraction of X-rays is commonly used in determining the structure of solids. X-rays have a wavelength that is comparable to the distance between atoms in a solid, making them ideal for determining the arrangement of atoms in a crystal lattice. Infrared, microwave, and visible radiation have longer wavelengths and are not suitable for this type of analysis.

Question 14

Solids having no ordered long-range structure are classified as

Accepted Answer

Solids that have no long-range order are called amorphous, such as glass or plastic. Crystalline solids have a regular arrangement of atoms, molecules, or ions in a three-dimensional repeating pattern. Metallic solids consist of metal atoms held together by metallic bonds, while molecular solids have atoms or molecules held together by van der Waals forces or hydrogen bonds.

Question 15

The vapor pressure of liquid chloroform,CHCl₃,is 400.0 torr at 24.1°C and 100.0 torr at -6.3°C.What is ΔH_vap of chloroform?

Accepted Answer

The Clausius-Clapeyron equation relates the vapor pressure of a substance at different temperatures to its heat of vaporization ($\Delta H_{vap}$). The equation in its linear form is:$$\ln\left(\frac{P_2}{P_1}\right) = -\frac{\Delta H_{vap}}{R}\left(\frac{1}{T_2} - \frac{1}{T_1}\right)$$Given:- $P_1 = 400.0 \, \text{torr}$ at $T_1 = 24.1°C = 297.25 \, K$ (converting from °C to K by adding 273.15)- $P_2 = 100.0 \, \text{torr}$ at $T_2 = -6.3°C = 266.85 \, K$First, convert pressures to atmospheres because the gas constant $R$ is often given in units that are compatible with atmospheres:- $P_1 = 400.0 \, \text{torr} \times \frac{1 \, \text{atm}}{760 \, \text{torr}}$- $P_2 = 100.0 \, \text{torr} \times \frac{1 \, \text{atm}}{760 \, \text{torr}}$Then, plug the values into the Clausius-Clapeyron equation and solve for $\Delta H_{vap}$:$$\ln\left(\frac{100/760}{400/760}\right) = -\frac{\Delta H_{vap}}{8.3145 \, \text{J/mol·K}}\left(\frac{1}{266.85} - \frac{1}{297.25}\right)$$Solving for $\Delta H_{vap}$ gives a value close to 30.1 kJ/mol, indicating that option B is correct.

Question 16

Arrange the following in order of increasing boiling point. CH₃CH₂OH CH₃CH₂CH₃ H₃C-O-CH₃ CH₃CH₂NH₂ I II III IV

Accepted Answer

The order of increasing boiling points is based on the strength of intermolecular forces. Ethanol (I) has hydrogen bonding, giving it the highest boiling point. Ethylamine (IV) also has hydrogen bonding but is weaker than ethanol. Dimethyl ether (III) has dipole-dipole interactions, and propane (II) has only van der Waals forces, giving it the lowest boiling point.

Question 17

The normal boiling point for HBr is higher than the normal boiling point for HCl.This can be explained by

Accepted Answer

HBr has a higher molecular weight than HCl, leading to larger dispersion forces, which increases its boiling point. Hydrogen bonding is not significant in either molecule due to the lack of a strongly electronegative atom bonded to hydrogen capable of hydrogen bonding, and while both have dipole-dipole interactions due to their polar bonds, the key difference in boiling points is attributed to the dispersion forces.

Question 18

How many atoms are in one body-centered cubic unit cell of a metal?

Accepted Answer

In a body-centered cubic (BCC) unit cell, there is one atom at each of the eight corners of the cube and one atom in the center. Each corner atom is shared among eight adjacent unit cells, so each contributes 1/8 of an atom to the unit cell, totaling 1 atom from the corners. The atom in the center is not shared and contributes fully, adding another atom. Therefore, the total is 2 atoms per unit cell.

Question 19

Which of the following compounds has the highest boiling point?

Accepted Answer

The highest boiling point compound among the given choices will have the strongest intermolecular forces (IMFs). The compound with the highest number of hydrogen bonds will have the strongest IMFs. Option A has one hydrogen bond. Option B has two hydrogen bonds. Option C has one dipole-dipole interaction. Option D has one hydrogen bond and multiple dipole-dipole interactions. Therefore, option B (HOCH₂CH₂OH) with two hydrogen bonds has the highest boiling point.

Question 20

Which of the following compounds forms a covalent network solid?

Accepted Answer

Covalent network solids are extremely hard and have extremely high melting and boiling points because of the strong covalent bonds holding the atoms together. Diamond (C) is an example of a covalent network solid. The other compounds listed do not form covalent network solids because they do not have a three-dimensional network of covalently bonded atoms. Li is a metal and forms a metallic solid, O₂ and CO₂ form molecular solids held together by intermolecular forces.

Quiz 10: Liquids,solids,and Phase Changes

How many atoms are in one face-centered cubic unit cell of a metal?

Which is classified as an amorphous solid?

Hydroquinone is an antioxidant that is also used as a photographic reducer and developer.The normal boiling point of hydroquinone is 310°C.Calculate the pressure at which hydroquinone will boil at 200°C given that its ΔHvap is 73.38 kJ/mol.

Which type of bonding does Mg form upon solidification?

Which of the following forms a molecular solid?

Which of the following statements is not consistent with the properties of a molecular solid?

While mercury is very useful in barometers,mercury vapor is toxic.Given that mercury has a ΔHvap of 59.11 kJ/mol and its normal boiling point is 356.7°C,calculate the vapor pressure in mm Hg at room temperature,25°C.

The wavelength of light used to observe an object must be ________ than the object itself.

Which of the following forms an ionic solid?

A crystalline solid of unknown origin forms an aqueous solution that conducts an electrical current.The solid has a high melting point and shatters when struck with a hammer.The solid is likely to be

A kitchen pressure cooker operates at 1.50 atm.The ΔHvap of water is 40.7 kJ/mol.What is the boiling point of water in the pressure cooker?

Which of the following compounds forms a covalent network solid?

The structure of a solid can be determined by diffraction of radiation in which region of the electromagnetic radiation spectrum?

Solids having no ordered long-range structure are classified as

The vapor pressure of liquid chloroform,CHCl3,is 400.0 torr at 24.1°C and 100.0 torr at -6.3°C.What is ΔHvap of chloroform?

Arrange the following in order of increasing boiling point. CH3CH2OH CH3CH2CH3 H3C-O-CH3 CH3CH2NH2 I II III IV

The normal boiling point for HBr is higher than the normal boiling point for HCl.This can be explained by

How many atoms are in one body-centered cubic unit cell of a metal?

Which of the following compounds has the highest boiling point?

Which of the following compounds forms a covalent network solid?

Hydroquinone is an antioxidant that is also used as a photographic reducer and developer.The normal boiling point of hydroquinone is 310°C.Calculate the pressure at which hydroquinone will boil at 200°C given that its ΔH_vap is 73.38 kJ/mol.

While mercury is very useful in barometers,mercury vapor is toxic.Given that mercury has a ΔH_vap of 59.11 kJ/mol and its normal boiling point is 356.7°C,calculate the vapor pressure in mm Hg at room temperature,25°C.

A kitchen pressure cooker operates at 1.50 atm.The ΔH_vap of water is 40.7 kJ/mol.What is the boiling point of water in the pressure cooker?

The vapor pressure of liquid chloroform,CHCl₃,is 400.0 torr at 24.1°C and 100.0 torr at -6.3°C.What is ΔH_vap of chloroform?

Arrange the following in order of increasing boiling point. CH₃CH₂OH CH₃CH₂CH₃ H₃C-O-CH₃ CH₃CH₂NH₂ I II III IV