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# A 200.-milliliter sample of CO2(g) is placed in a sealed, rigid cylinder with a movable piston at 29

NY Regents Chemistry Exam June 2019

Questions 58-61

A 200.-milliliter sample of CO2(g) is placed in a sealed, rigid cylinder with a movable piston at 296 K and 101.3 kPa.

58 State a change in temperature and a change in pressure of the CO2(g) that would cause it to behave more like an ideal gas. 

Solution: Real gases behave most like ideal gases at a high temperature and low pressure.

Answer: increase the temperature and decrease the pressure

59 Determine the volume of the sample of CO2(g) if the temperature and pressure are changed to 336 K and 152.0 kPa. 

Solution: According to the combined gas law which can be found in Table T on the Reference Table, P1V1/T1 = P2V2/T2.

P1 = 101.3 kPa P2= 152.0 kPa.

V1 = 200.-ml V2 = ?

T1 = 296 K T2 = 336 K

We can plug in the values into the equation to calculate V2

60 State, in terms of both the frequency and force of collisions, what would result from decreasing the temperature of the original sample of CO2(g), at constant volume. 

Solution and answer: Decreasing the temperature results in decreased frequency and force of collisions.

61 Compare the mass of the original 200.-milliliter sample of CO2(g) to the mass of the CO2(g) sample when the cylinder is adjusted to a volume of 100. milliliters. 

Solution: Changing the volume or temperature or pressure of a sample does not change its mass. Only adding or removing mass will result in a mass change.

Answer: the mass stays the same