Chemistry 1A - Spring 2010 - Nitsche - Midterm 3 Solutions

Chemistry 1A - Spring 2010 - Nitsche - Midterm 3 Solutions...

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Unformatted text preview: Chemistry 1A, Spring 2010 Midterm 3 Solutions Apr 12, 2010 Problems 1. A 1.00 mol sample of CO 2 gas is confined in a 20.0 liter container at 25 ◦ C. If 1.00 mol of H 2 gas is added, holding the volume and temperature constant, the average kinetic energy of the system will ? A) Increase B) Decrease C) Remain the Same D) Not enough information to answer the question. Kinetic energy depends only on the temperature, so it will remain the same as temperature is held constant. 2. The average kinetic energy of the particles of a gas is directly proportional to ? A) the rms speed B) the square of the rms speed C) the square root of the rms speed D) the square of the particle mass 3 2 RT = E kin = 1 2 mv 2 rms 3. According to the kinetic-molecular theory, in which of the following gases with the root-mean-square speed of the molecules be the highest at 200 ◦ C? A) HCl B) Cl 2 C) H 2 O D) SF 6 E) None. The molecules of all gases have the same root-mean-squared speed at any given temperature. Water is the lightest of the choices. Since they will all have the same kinetic energy (as they are at the same temperature), the lightest gas must have the highest velocity, as v rms ∝ r T M 4. According to the kinetic-molecular theory, if the temperature of a gas is raised from 100 ◦ C to 200 ◦ C, the average kinetic energy of the gas will ? A) double B) increase by a factor of 1.27 C) increase by a factor of 100 D) decrease by half E) decrease by a factor of 100 1 Kinetic energy depends only on temperature. However, we must use the Kelvin scale, as it is an absolute scale, and we know that kinetic energy cannot be below zero. 100 ◦ C + 273 = 373 K 200 ◦ C + 273 = 473 K E kin,f E kin,i = 3 2 RT f 3 2 RT i = T f T i = 473 K 373 K = 1 . 27 Therefore, E kin,f is 1.27 times larger than E kin,i 5. Which of the following is NOT part of the kinetic-molecular theory? A) Atoms are neither created nor destroyed by ordinary chemical reactions. B) Attractive and repulsive forces between gas molecules are negligible. C) Gases consist of molecules in continuous, random motion. D) Collisions between gas molecules do not result in the loss of energy. E) The volume occupied by all of the gas molecules in a container is negligible compared to the volume of the container. Kinetic-molecular theory has only to do with gases, not chemical reactions. 6. Which of the following statements is true for ideal gases, but it not always true for real gases? Mark all that apply. A) Collisions between molecules are elastic B) The size of molecules is unimportant compared to the distance between them. C) The volume occupied by the molecules is negligible compared to the volume of the container....
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This note was uploaded on 03/16/2011 for the course CHEM 10953 taught by Professor Pines during the Fall '11 term at Berkeley.

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Chemistry 1A - Spring 2010 - Nitsche - Midterm 3 Solutions...

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