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. [1]

**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. [1]

**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

Answer: 151 mL

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. [1]

**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. [1]

**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

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