Quiz 5/4/04 For what purpose is a manometer used? Explain how a gas exerts pressure on its container. Which gas exerts less pressure, the one on the right or the left? What is the value of standard atmospheric pressure in kPa. If the difference in height in the manometer on the left is 25 mm, and atmospheric pressure is 100 kPa, what is the pressure of the gas in the left manometer? Convert 25oC to Kelvins. A manometer is used to measure gas pressure. Gas molecules bounce against the sides of the container, Pressure = Force/Area therefore, the more collisions, the more pressure. The gas on the left exerts less pressure 101.3 kPa Pgas = 100 – 25/7.5 Pgas = 97 kPa 25oC + 273 = 298 K

States of matter most movement Gases form when atoms do not have enough attractive force to stay near each other. Gases move rapidly filling the entire container. least movement Solids are organized structures with lots of attraction and little “freedom” to move Liquids consist of disorganized atoms/molecules which are attracted to each other.

Test Tomorrow Today: To study for the test, write three questions and their answers. a question about an open ended manometer, including a calculation. a question about a closed end manometer, including a calculation. a question relating kelvin temperatures to celcius temperatures. extra credit : 5 simple questions.

# 25. An open manometer like the one in figure 15 # 25. An open manometer like the one in figure 15.4 is used to measure the pressure of a gas sample. The mercury level is 12 mm higher in the gas sample arm. What is the pressure, in kilopascals, of the gas in the container if the air pressure is 98.7 kilopascals? Patm = 98.7 – 12/7.5 Patm = 97.1 kPa

# 26. In a closed manometer, assume that the height of the levels differs by 522 mm Hg. What is the pressure, in kilopascals, of the gas in the container? Pgas = 522/7.5 Pgas = 69.6 kPa Answers to the rest of the questions are: 27. 103.5 kPa 28. 106.7 kPa 29. The temperature increases directly (proportionally) with an increase in Kinetic energy. 30. Absolute zero means all molecular motion ceases (stops). Homework where work is shown only merits ½ credit!

More practice. a. 186K b. 192 K c. 433 K d. 421 K e. 894 K = -87oC Which gas moves slowest, at Standard Temperature and Pressure? 12. N2 = 28g/mole F2 = 38 g/mole CO2 = 44g/mole O2 = 32 g/mole - 273K - 273K 10. a. 123oC b. -90oC c. 18oC d. 25oC + 273K = 396 K + 273K = 331 K + 273K = 291 K N2 moves the fastest because it weighs the least. CO2 moves slowest. + 273K = 298 K