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# Gas Laws

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Instructions: Read each question carefully. Choose the answer that best fits the question. For any calculation questions, you must show all your math work.

1.
A large truck passes a car on the highway. According to Bernoulli's principle, which of the following should occur?
1. Pressure decreases between the vehicles, so the car and truck move slightly apart.
2. Pressure decreases between the vehicles, so the car and truck move slightly together.
3. Pressure increases between the vehicles, so the car and truck move slightly apart.
4. Pressure increases between the vehicles, so the car and truck move slightly together.
2.
The particles in a ideal gas interact with each other only by perfectly elastic collisions that exchange energy and momentum.
1. True
2. False
3.
Using the Ideal Gas Law equation, $PV=N*k_b*T$, determine the number of particles of air contained in one cubic meter at an atmospheric pressure of 101,325Pa and a temperature of $293degK$.
• $N=(P*V)/(k_b*T)$

$N=(101,325Pa*1m^3)/(1.38*10^-23*293degK)$

$N=2.5*10^25$ molecules
4.
A real gas most closely approaches the behavior of an ideal gas under conditions of
1. low P and T.
2. STP.
3. high P and low T.
4. high P and T.
5. low P and high T.
5.
Suppose a car tire were inflated to a gauge pressure of 32 psi (absolute pressure is therefore 46.7 psi) at $30degC$. The car is parked in the street as a cold front hits over night, and the temperature drops to $5degC$. What is the new gauge pressure in the tire?
• $P_1T_2=P_2T_1$

$46.7"psi"*278degK=P_2*303degK$

$P_2=[(12982.6"psi"degK)]/(303degK)$

$P_2=42.84"psi"$

$P_2" of the gauge"=42.84"psi"-14.7"psi"=28.1"psi"$
6.
Gay-Lussac's Law states that the pressure of a gas is directly proportional to the absolute temperature for a fixed mass of gas held at a constant volume.
1. True
2. False
7.
The ideal gas law predicts that the molar volume (volume of one mole) of gas equals
1. (MW)P/RT.
2. gRT/PV.
3. RT/P.
4. 1/2ms-2.
5. 22.4 L at any temperature and pressure.
8.
According to Boyle's Law, in a gas at a constant temperature, the change in pressure is inversely proportional to to the change in volume. This relationship can be expressed as an equation, $P_1//P_2=V_2//V_1$. If 250mL of a gas, at a pressure of 214mmHg and a constant temperature, is forced into a 105mL rigid container, what will the final pressure be in mmHg?
• $P_1V_1=P_2V_2$

$214mmHg*0.250L=P_2*0.105L$

$P_2=(53.5L*mmHg)/(0.105L)$

$P_2=509.52mmHg$
9.
Which property of fluids accounts for why a gas will expand to fill any container, thereby changing the pressure and temperature?
1. viscosity
2. compressibility
3. expandabilty
4. hydrostatics
10.
Under conditions of fixed volume and amount of gas, Gay-Lussac's law requires that

I. $P_1T_2=P_2T_1$.

II. PT = constant.

III. $P_1/T_1=P_2/T_2$.
1. I only
2. II only
3. III only
4. I and III
5. I, II, and III
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