Physical Chemistry - Problem Drill 01: Chemistry and Physics Review

Transcription

1 Physical Chemistry - Problem Drill 01: Chemistry and Physics Review No. 1 of Chemical bonds are considered to be the interaction of their electronic structures of bonding atoms involved, with the focus mainly on valence electrons. The best understanding of chemical bonds comes from. (A) Polar covalent bond theory (B) Ionic bond theory (C) Covalent bond theory (D) Computational Chemistry (E) None of the above is correct. Good try. Hint: Think about the way bond theories have been evolved to modern electronic structure theories. Good try. Hint: Think about the way bond theories have been evolved to modern electronic structure theories. Good try. Hint: Think about the way bond theories have been evolved to modern electronic structure theories. D. Correct! Good work. Chemical bonds are best described by computational chemistry, modern electronic structure methods. Good try. Hint: Think about the way bond theories have been evolved to modern electronic structure theories. Correct Answer: D The Best Understanding of Chemical Bonds comes from Computational Chemistry, using computers to solve approximate, Quantum Mechanical, equations for molecules.

2 No. 2 of The main intermolecular forces are Van der Waals interactions, which are attraction forces. Among them, non-polar molecules attract non-polar molecules by. (E) Electron sharing. A. Correct! Good work. Non-polar molecules attract non-polar molecules by induced-dipoleinduced-dipole forces. The force between two instantaneously induced dipoles called London dispersion force. Good try. Hint: Think about instantaneous electron distributions in molecules. Good try. Hint: Think about instantaneous electron distributions in molecules. Good try. Hint: Think about instantaneous electron distributions in molecules. Good try. Hint: Think about instantaneous electron distributions in molecules. Correct Answer: A Non-polar molecules attract non-polar molecules by induced-dipole-induced-dipole forces. Normal electron motion in a nonpolar molecule creates temporary dipoles to which neighboring molecules respond with complimentary temporary dipoles.

3 No. 3 of Polar molecules have uneven spread of electron density while nonpolar molecules share electrons equally between the bonding atoms. Polar molecules (HF) attract nonpolar molecules (H 2 ) by. (E) Electron sharing. Good try. Hint: Think about instantaneous electron distributions in molecules and permanent dipoles in molecules. B. Correct! Good work. Polar molecules attract non-polar molecules by dipole-induced-dipole forces. Good try. Hint: Think about instantaneous electron distributions in molecules and permanent dipoles in molecules. Good try. Hint: Think about instantaneous electron distributions in molecules and permanent dipoles in molecules. Good try. Hint: Think about instantaneous electron distributions in molecules and permanent dipoles in molecules. Correct Answer: B Polar molecules attract non-polar molecules by dipole-induced-dipole forces. When a polar molecule like HF approaches a nonpolar molecule like H 2 a dipole-induceddipole force occurs due to an induced dipole in the H 2 molecule caused by the presence of the dipole of the HF molecule.

4 No. 4 of Polar molecules interact with one another. This interaction is governed by the fact that like charges repel and opposite charges attract. Polar molecules (H 2 O) attract polar molecules (NH 3 ) by. (E) Electron sharing. Good try. Hint: Think about permanent dipoles in molecules. Good try. Hint: Think about permanent dipoles in molecules. C. Correct! Good work. Polar molecules attract polar molecules by dipole-dipole forces. Good try. Hint: Think about permanent dipoles in molecules. Good try. Hint: Think about permanent dipoles in molecules. Correct Answer: C Polar molecules attract polar molecules by dipole-dipole forces. Polar molecules have unbalanced electron distributions making them electric dipoles. When polar molecules, such as ammonia, are added to another polar molecules such as water, ammonia dissolves because of the interaction between the two types of molecules.

5 No. 5 of An ionic bond is a chemical bond in which one atom loses an electron to form a positive ion and the other atom gains an electron to form a negative ion. Such a bond is the result of. (E) Electron sharing. Good try. Hint: Think about the formations of anions and cations. Good try. Hint: Think about the formations of anions and cations. Good try. Hint: Think about the formations of anions and cations. D. Correct! Good work. An ionic bond is the result of ion-ion forces. Good try. Hint: Think about the formations of anions and cations. Correct Answer: D An ionic bond is a type of chemical bond formed through an electrostatic attraction between two oppositely charged ions. Ionic bonds are formed between a cation, which is usually a metal, and an anion, which is usually a non-metal. Ionic bonds are the result of electron transfer between atoms. The larger the difference between the electronegativity of the two atoms, the more ionic the bond is. Ion-ion forces are the strongest forces, leading to solids with high melting points, such as table salt Na + ---Cl -.

6 No. 6 of Covalent bonds are forces that hold atoms together, typically two non-metallic elements in a molecule. A covalent bond (C-C) is the result of. (E) Electron sharing. Good try. Hint: Think about the nature of a chemical bond. Good try. Hint: Think about the nature of a chemical bond. Good try. Hint: Think about the nature of a chemical bond. Good try. Hint: Think about the nature of a chemical bond. E. Correct! Good work. A covalent bond is the result of electron sharing. Correct Answer: E Covalent Bonds are the result of electron sharing between atoms. Nonpolar covalent bonds are the result of even electron sharing, while polar covalent bonds are the result of unequal electron sharing between atoms. Actually, all bond types (ionic or covalent) involve some extent of electron sharing. According to the electronic structure theories, it is the orbital overlap that forms a covalent bond.

7 No. 7 of In physical chemistry, the Van der Waals force is the sum of the attractive or repulsive forces between molecules (or between parts of the same molecule) other than those due to covalent bonds, the hydrogen bonds, or the electrostatic interaction of ions with one another or with neutral molecules. Van der Waals Forces include. (E) A, B and C. Good try. Hint: Look for a more complete answer. Good try. Hint: Look for a more complete answer. Good try. Hint: Look for a more complete answer. Good try. Hint: Think about intermolecular forces. E. Correct! Good work. Van der Waals Forces include: induced-dipole-induced-dipole forces, dipole-induced-dipole forces, and dipole-dipole forces. Correct Answer: E Van der Waals Forces include: induced-dipole-induced-dipole forces, dipoleinduced-dipole forces, and dipole-dipole forces. These forces namely are: - Keesom Force: Force between two permanent dipoles - Debye Force: Force between a permanent dipole and a corresponding induced dipole - London Dispersion Force: Force between two instantaneously induced dipoles

8 No. 8 of Refraction is the change in direction of a wave due to a change in its medium. Refraction depends on. (A) The viscosity of a material. (B) The speed of sound in different materials. (C) The frequency of light. (D) The wavelength of light. (E) The speed of light in different materials. Good try. Hint: Think about the refractive index of a material. Good try. Hint: Think about the refractive index of a material. Good try. Hint: Think about the refractive index of a material. Good try. Hint: Think about the refractive index of a material. E. Correct! Good work. Refraction depends on the speed of light in different materials. Correct Answer: E Refraction depends on the speed of light in different materials. Light changes direction by Refraction, as it passes from one material into another depending on the speed of light in the two materials. Due to change of medium, the phase velocity of the wave is changed but its frequency remains constant. This is most commonly observed when a wave passes from one medium to another at any angle other than 90 or 0.

9 No. 9 of Electromagnetic radiation is a form of energy emitted and absorbed by charged particles, which exhibits wave-like behavior as it travels through space. Electromagnetic radiation is associated with. (A) The speed of light. (B) An oscillating electric wave. (C) An oscillating magnetic wave. (D) Static electric and magnetic fields. (E) A, B, and C. Good try. Partially correct. Hint: Look for a more complete answer. Good try. Partially correct. Hint: Look for a more complete answer. Good try. Partially correct. Hint: Look for a more complete answer. Good try. Hint: Think about oscillating fields. E. Correct! Good work. Electromagnetic radiation is associated with: the speed of light, an oscillating electric field, and an oscillating magnetic field. Correct Answer: E Electromagnetic Radiation, light, is an example of waves, which is made up of electric wave and a magnetic wave. Electromagnetic Radiation travels through empty space at the Speed of light. EMR has both electric and magnetic field components, which stand in a fixed ratio of intensity to each other, and which oscillate in phase perpendicular to each other and perpendicular to the direction of energy and wave propagation. In a vacuum, electromagnetic radiation propagates at a characteristic speed, the speed of light.

10 No. 10 of Energy is associated with its applied force. Force is. (A) The negative rate of change of Potential Energy with respect to position in the direction of a Force. (B) The positive rate of change of Potential Energy with respect to position in the direction of a Force. (C) The negative rate of change of Kinetic Energy with respect to position in the direction of a Force. (D) All of the above are correct. (E) None of the above is correct. A. Correct! Good work. Force is the negative rate of change of Potential Energy with respect to position in the direction of a Force. Good try. Hint: Think about the relationship between a force and potential energy, with examples of such as a spring or gravity acted by its restoring force. Good try. Hint: Think about the relationship between a force and potential energy, with examples of such as a spring or gravity acted by its restoring force. Good try. Hint: Think about the relationship between a force and potential energy, with examples of such as a spring or gravity acted by its restoring force. Good try. Hint: Think about the relationship between a force and potential energy, with examples of such as a spring or gravity acted by its restoring force. Correct Answer: A In physics, potential energy is the energy of an object or a system due to the position of the body or the arrangement of the particles of the system. Force is the negative rate of change of potential energy with respect to position in the direction of a force. Force can be calculated with the equation: de F dx p