Gas Laws Standard 4 Review answers

The kinetic molecular theory describes the motion of atoms and molecules and explains the properties of gases. As a basis for understanding this concept: a. Students know the random motion of molecules and their collisions with a surface create the observable pressure on that surface. 1. Which is NOT true about gases? a. they are made of very small particles c. they collide elastically b. electrostatic attraction pulls them together d. they are in constant motion 2. What is pressure? a. the volume of a gas c. the force created by collisions of gas particles b. a measure of kinetic energy d. a concentration of molecules 3. Which is NOT a standard pressure? a. 3 atm b. 760 torr c KPa d. 1 atm 4. When a cold tire is inflated to a certain pressure and then is warmed up due to friction with the road, the pressure increases. This happens because the: A air molecules hit the walls of the tire less frequently. B rubber in the tire reacts with oxygen in the atmosphere. C air molecules speed up and collide with the tire walls more often. D air molecules diffuse rapidly through the walls of the tire.

5. What causes the pressure on the inside walls of this container? A charge of the gas molecules in the container B temperature of the gas molecules in the container C collision of the gas molecules on the container D weight of the gas molecules on the container 6. What causes a balloon to hold its shape? A random motion of gas molecules B collision of gas molecules against a balloons’ wall C weight of the gas molecules inside of the balloon D energy held by each gas molecules within the balloon

b. Students know the random motion of molecules explains the diffusion of gases. 5. The movement of molecules from areas of high concentration to low concentration is a. molarity b. temperature c. potential energy d. diffusion 6. When someone standing at one end of a large room opens a bottle of vinegar, it may take several minutes for a person at the other end to smell it. Gas molecules at room temperature move at very high velocities, so what is responsible for the delay in detection of the vinegar? A the increase in the airspace occupied by vinegar molecules B the chemical reaction with nerves, which is slower than other sensory processes C attractive forces between the air and vinegar molecules D random collisions between the air and vinegar molecules 7. Methane (CH 4 ) gas diffuses through air because the molecules are A moving randomly. B dissolving quickly. C traveling slowly. D expanding steadily. 7. Which is an example of diffusion? A disappearance of a puddle in sunlightB smell of a rotten egg across a room C boiling of water D balloon that shrinks when it becomes cold

c. Students know how to apply the gas laws to relations between the pressure, temperature, and volume of any amount of an ideal gas or any mixture of ideal gases. 8. As volume increases, what happens to the pressure of the gas in a container? It a. decreases b. increases c. it stays the same 9. I fill a balloon with 2L of air at 27 degrees Celsius and at 1.5 atm. If I move the balloon to STP (1 atm and O C), what volume will it be at? 1) write the combined gas law 2) Replace letters with numbers from the word problem (don’t forget to convert celsius to K before plugging in) K and O +273 = 273 K (STP) 3) cross multiply (300)(1)V 2 = (1.5)(2)(273) 4)and solve for V = 2.73 L P 1 V 1 = P 2 V 2 T 1 T 2 (1.5) (2) = (1)V 2 (300) 273

10. I fill a scuba tank with 15L of air at a pressure of kPa. At the bottom of the ocean, the pressure is 350 kPa. Assuming that I don’t breathe any of the air, how much volume is in my tank? 1.Read problem and identify all numbers given (ie what is 15L (it’s V1) and what is kPa (it’s P1) etc) 2.Write the combined gas law 3.Cross out any variable you don’t need, just make sure to do this on both sides. Since this problem does not discus temperature my new gas law is 4.Now replace letters with numbers and solve. (101.3) (15) = (350) V 2, so V 2 = 4.34 L P 1 V 1 = P 2 V 2 T 1 T 2 P 1 V 1 = P 2 V 2

11. If I cut the temperature in half, what will happen to the pressure? It a. doubles b. nothing c. becomes half d. triples 12. The volume of 400 mL of chlorine gas at 400 mm Hg is decreased to 200 mL at constant temperature. What is the new gas pressure? A 400 mm HgB 300 mm HgC 800 mm HgD 650 mm Hg 1) Identify all numbers in word problem 2) Write the combined gas law and cross out any variables not needed 3) Your new gas law should be 4) Plug and chug. (400)(400) = P 2 (200) P2 = 800 mmHg P 1 V 1 = P 2 V 2

13. Under what circumstance might a gas decrease in volume when heated? A The gas is held constant at STP. B The gas remains under uniform temperature. C The gas is placed under increasing pressure D The gas undergoes a decrease in pressure. 14. A sample of carbon dioxide gas occupies a volume of 20 L at standard temperature and pressure (STP). What will be the volume of a sample of argon gas that has the same number of moles and pressure but twice the absolute temperature? 1)Identify all numbers given in word problem. Standard temperature is 273 K. 2)Write the combined gas law and cross out unneeded variables from both sides 3)Your new gas law is 4)Replace letters with numbers _20_ = _V 2 __ (T 2 = 546 because it says the new temp is twice the original) ) Cross multiply so (273) V 2 = (20)(546) and solve for V 6) V 2 = 40L V 1 = _V 2 T 1 T 2

15. How are pressure and volume of gas related? A as pressure decreases, volume increases. B as pressure increases, volume increases C as pressure decreases, volume decreases. D pressure and the volume are not related. 16. Under which of the following sets of conditions will a 0.50 mole sample of helium occupy a volume of 11.2 liters? A 298 K and 0.90 atmB 273 K and 1.10 atm C 373 K and 0.50 atmD 273 K and 1.00 atm 1)0.5 mole in 11.2 L is the same as 1 mole in 22.4L. To have one 1 mole at 22.4 L it has to be STP which is D

17. What is the standard temperature in Celsius? O In Kelvin? Standard temperature and pressure (STP) are defined as A 0 ºC and 1.0 atm pressure.B 0 ºC and 273 mm Hg pressure. C 0 K and 1.0 atm pressure.D 0 K and 760 mm Hg pressure. Convert each of the following: (formula to convert is given on reference page. K = C) K = -73°C K = -228°C K = 50 °C K = -75 °C 26. What is the equivalent of 423 kelvin in degrees Celsius? A – 223 ºCB – 23 ºCC 150 ºCD 696 ºC

f. Students know there is no temperature lower than 0 Kelvin. Explain using words what absolute zero is. 27. Explain using words what absolute zero is. The temperature at which all motion stops 28. What temperature is absolute zero at? -273 o C or 0K 29. A student works a gas law problem and determines that the answer for temperature is -25K. Is that possible? Explain. No because the 0K is the lowest Kelvin temperature 30. Theoretically, when an ideal gas in a closed container cools, the pressure will drop steadily until the pressure inside is essentially that of a vacuum or O atm. At what temperature should this occur? A 0ºCB −460 ºCC −273 KD 0 K 31. The temperature at which all molecular motion stops is A −460 ºC.B −273 K.C 0 K.D 0C.

32. What is temperature?A measurement of the kinetic energy (energy of motion) of particles 33. If I increase the temperature of a gas, what will the molecules do? The begin to move faster and collide more frequently h* Students know how to solve problems by using the ideal gas law in the form PV = nRT. R= atm * L/mol * K 34. I have 2 moles of Kr gas at 30 °C and a pressure of 2.5 atm. What is the volume? PV = nRT, plug and chug ( = 303K) (2.5) V = (2) (0.082) (303)V = 19.8 L