MIDTERM REVIEWER IN GENCHEM2

To create a viable artificial blood, what properties of water must be mimicked to ensure efficient oxygen delivery to the body's cells and tissues?

• high viscosity and low surface tension

• low boiling point and high vapor pressure

• high specific heat capacity and low density

• high polarity and the ability to form hydrogen bonds

Answer explanation

Water's high polarity and ability to form hydrogen bonds are essential for its role in oxygen transport. These properties allow water to dissolve oxygen, maintain blood fluidity, and regulate body temperature, all of which are crucial for life.

Therefore, when designing artificial blood, mimicking these properties of water is crucial for creating a viable substitute that can effectively transport oxygen throughout the body.

Considering the importance of intermolecular forces, what molecular characteristics would make a solvent suitable for a high-temperature industrial process, requiring high boiling point, low viscosity, and non-toxicity?

• Large, polar molecules with strong hydrogen bonding

• Ionic compounds with strong electrostatic interactions

• Small, polar molecules with moderate dipole-dipole interactions

• Small, nonpolar molecules with weak London Dispersion Forces

Answer explanation

Small, polar molecules with moderate dipole-dipole interactions offer a balance between:

High Boiling Point: Ensuring the solvent remains liquid at high temperatures.

Low Viscosity: Facilitating efficient pumping.

Non-Toxicity: Meeting safety requirements.

This combination makes them ideal candidates for high-temperature industrial solvents.

If a substance exhibits a short plateau on its heating curve during the liquid-to-gas transition, what does this suggest about the strength of its intermolecular forces and its boiling point?

• It has a low boiling point. 

• It has a high melting point.

• It has a low heat of vaporization.

• It has a high heat of vaporization.

Answer explanation

A short plateau on the heating curve during the liquid-to-gas phase transition indicates that the substance has a low heat of vaporization. This is because the substance requires less energy to overcome the weak intermolecular forces holding its molecules together in the liquid state and transition into the gas state.

A material exhibits directional properties, being malleable in one direction and brittle in another. What does this suggest about its atomic arrangement?

• amorphous solid

• crystalline solid with non-directional bonds

• crystalline solid with highly directional bonds

• mixture of crystalline and amorphous phases

Answer explanation

The material described is likely a composite material, exhibiting a mixture of crystalline and amorphous phases. The crystalline phase, with its ordered atomic arrangement, contributes to the material's malleability in one direction, while the amorphous phase, lacking long-range order, leads to brittleness in the perpendicular direction. This combination of structures is common in polymers and can also be found in metals subjected to specific processing techniques. The presence of both crystalline and amorphous phases within the material's structure explains its unique anisotropic properties.

What structural feature is common to metals that exhibit high malleability, ductility, and electrical conductivity?

• amorphous solid with isotropic properties

• crystalline solid with non-directional bonds

• crystalline solid with highly directional bonds

• amorphous solid with highly directional bonds

Answer explanation

Metals are crystalline solids with non-directional metallic bonds. This structure allows for the free movement of electrons, contributing to their excellent electrical conductivity, and the ability of the atoms to slide past each other, leading to their high malleability and ductility.

Which segment represents that the substance is melting?

• BC

• CD

• DE

• AB

Answer explanation

The ice cube starts to melt from point B and ends with point C. Since there is no change in

temperature during phase changes, segment BC, as well as other phase changes, appears

horizontal in the phase diagram.

Which of the following segments represents an increase in temperature of the gaseous substance?

• DE

• CD

• EF

• AB

Answer explanation

Segment EF represents a change in temperature of steam from 100 degC to 125 degC.

A molecule is synthesized with both polar and nonpolar regions, and it contains an -OH group. What types of intermolecular forces would be most important in this molecule, and how would these forces influence its behavior?

• Only London Dispersion Forces; they would be the dominant force.

• Ion-dipole forces and hydrogen bonding; ion-dipole forces would be dominant.

• Dipole-dipole forces and London Dispersion Forces; dipole-dipole forces would be dominant.

• Hydrogen bonding and London Dispersion Forces; hydrogen bonding would be the dominant force, with London Dispersion Forces contributing.

Answer explanation

The molecule will exhibit both hydrogen bonding and London Dispersion Forces, but hydrogen bonding will be the primary force due to its strength and the presence of the -OH group. This means that hydrogen bonding will play a larger role in determining the molecule's interactions and properties.

Water and carbon dioxide are both heated from a temperature below their triple point to a temperature above their critical point, at a constant pressure. Which substance will undergo a solid-liquid-gas phase transition, and which will undergo a direct solid-gas transition?

• Both will transition from solid to gas

• Both will transition from solid to liquid to gas

• Water will transition from solid to liquid to gas; carbon dioxide will transition from solid to gas

• Water will transition from solid to gas; carbon dioxide will transition from solid to liquid to gas

Answer explanation

Water, when heated under the specified conditions, will undergo a complete phase transition sequence: solid (ice) to liquid (water) to gas (steam).

Carbon dioxide, under the same conditions, will undergo sublimation, transitioning directly from solid (dry ice) to gas (carbon dioxide).

A new material is being designed to exhibit superhydrophobicity, meaning it will strongly repel water. Considering the nature of water and the forces that govern its interactions, what specific characteristics should this material possess to achieve this high level of water repellency?

• have a high density and low surface energy

• be nonpolar and have a rough surface texture

• low specific heat capacity and high thermal conductivity

• be highly polar and able to form hydrogen bonds with water

Answer explanation

Think of a lotus leaf. Its surface is covered with tiny, nonpolar waxes and has a rough, micro-structured texture. This combination of properties creates a superhydrophobic surface that repels water droplets, allowing them to bead up and roll off easily.

The combination of these two factors, a nonpolar surface and a rough texture, is essential for achieving superhydrophobicity.