Homework Help for Chemistry (page 7)
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The excess internal energy of metabolism is exhausted through a variety of channels, such as through radiation and evaporation of perspiration. Consider another pathway for energy loss: moisture in exhaled breath. Suppose you breathe out 22.0 breaths per minute, each with a volume of 0.600 L. Suppose also that you inhale dry air and exhale at 37oC containing water vapor with a vapor pressure of 3.20 kPa. The vapor comes from the evaporation of liquid water in your body. Model the water vapor as an ideal gas. Assume its latent heat of evaporation at 37oC is the same as its heat of vaporization at 100oC. Calculate the rate at which you lose energy by exhaling humid air.
The arrow OA in the PV diagram shown in Figure OQ22.11 represents a reversible adiabatic expansion of an ideal gas. The same sample of gas, starting from the same state O now undergoes an adiabatic free expansion to the same final volume. What point on the diagram could represent the final state of the gas? (a) the same point A as for the reversible expansion, (b) point B, (c) point C, (d) any of the choices, and (e) none of those choices.
An ionized oxygen molecule (O+2) at point A has charge +e and moves at 2.00×103 m/s in the positive x-direction. A constant electric force in the negative x-direction shows the molecule to a stop at point B, a distance of 0.750 mm past A on the x-axis. Calculate (a) the x-component of the electric field and (b) the potential difference between points A and B.
You are working as a research assistant for a professor whose research area is thermodynamics. He points out to you that Daniel Fahrenheit used the best estimate of normal human body temperature as one of the points in defining the original Fahrenheit temperature scale. On the revised scale we now use, normal human body temperature is 98.6oF. Your professor proposes a new scale on which normal human body temperature would be exactly 100oN, where the unit oN is a degree on the New scale. The temperature of freezing water would be 0oN, as on the Celsius scale. Your professor asks you to determine the following temperatures on his new scale: (a) absolute zero, (b) the melting point of mercury (-37.9oF), (c) the boiling point of water, and, for publicity at his expected future press conference, (d) the highest recorded air temperature on the Earth's surface. 134.1oF on July 10, 1913, in Death Valley, California.
Case Study: Nitrous oxide (N2O) is a gas commonly used for its anesthetic effects in dentistry or surgery. When it interacts with oxygen, nitrous oxide gives rise to nitric oxide (NO), which will interact with ozone. Thus, nitrous oxide is a greenhouse gas that affects the ozone layer in our stratosphere. Suppose a container contains 3 mol of nitrous oxide, where the rms speed of the molecules in the container is 411.1 m/s. What is the average kinetic energy of the molecules inside the gas?
Substance A has twice the specific heat of substance B. Equal masses of two substances, at different temperatures, are placed in thermal contact and allowed to come to equilibrium. (a) What is the ratio QB/QA of the energy transferred to (or from) the samples? (Hint: Remember to include the correct signs.) (b) What is the ratio of their temperature changes?
Temperature differences on the Rankine scale are identical to differences on the Fahrenheit scale, but absolute zero is given as 0oR. (a) Find a relationship converting the temperatures of TF of the Fahrenheit scale to the corresponding temperatures TR of the Rankine scale. (b) Find a second relationship converting temperatures TR of the Rankine scale to the temperatures TK of the Kelvin scale.
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