Be careful of units! All the conversions you need are in the information section
ID: 1410142 • Letter: B
Question
Be careful of units! All the conversions you need are in the information section of the lab.
Suppose the volume of the syringe is 40.2 cc. You measure the pressure as 1.14 atm, and the temperature as 24.2o C. Assume: the diameter of the plunger on the syringe is 2.44 cm.
a)Find - the number of moles of gas in the syringe
n =_______ moles
- the number of molecules of gas in the syringe.
N = _______ molecules
- the mass of air in the syringe. (Use the molar mass of air given in the information section of the lab.)
mair = _______ kg
b)Supose you push down the syringe so the volume is now 37.0 cc, with the temperature remaining unchanged. Find: - the new pressure inside the syringe.
P = ________ atm
- the magnitude of the force exerted by the gas on the plunger of the syringe.
F = _______ N
c) Suppose you suddenly press down on the syringe so the volume is now 23.3 cc, and plunge it into cold water. When the temperature is 8.69o C, find the pressure inside the syringe.
P = _______ atm
Explanation / Answer
a) the number of moles of gas in the syringe = PV/RT
= (1.14 * 0.0402)/(0.0821 * 297.35)
= 1.877 * 10-3 moles
number of molecules of gas in the syringe = 6.023 * 1023 * 1.877 * 10-3
= 1.1305 * 1021 molecules
mass of air in the syringe = 1.877 * 10-3 * 0.028
= 5.255 * 10-5 kg
b) the new pressure inside the syringe = 40.2 * 1.14/37 = 1.238 atm
magnitude of the force exerted by the gas = 101325 * 1.238 * (3.14 * 0.0122 * 0.0122)
= 58.625 N
c) the pressure inside the syringe = 1.877 * 10-3 * 0.0821 * 281.84/0.0233
= 1.864 atm
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