Boyle's law states that P X V before a gas is compressed or expanded equals P X V afterwards . This gives a formula very like the one for moments: P1 X V1 = P2 X V2 . Suppose a gas is in a container of volume 5 l at a pressure of 2000 Pa, and then the piston is pushed down, squeezing the gas to a volume of 3.5 l. What pressure will the gas now be producing? Using the formula: P1 X V1 = P2 X V2
2000 Pa X 5 l = P2 X 3.5 l
2000 Pa X 5 l = P2
3.5 l
P2 = 2860 Pa
Now do as many of these as you can; work in whatever units are given:
1. 6 m3 of a gas is at a pressure of 500 Pa. If the pressure was reduced to 250 Pa, what will the volume expand to? (2)
2. 6 m3 of gas is at a pressure of 500 N/m2. If the volume of the gas is decreased to 2 m3 what will the pressure increase to? (2)
3. 4 cm3 of air is at a pressure of 100 000 Pa. If the pressure is increased to 250 000 Pa, what will the volume of air decrease to? (3)
4. In a Boyle's law experiment the trapped air occupies a column 28 cm long when the pressure on it is 110 000 Pa.
(i) If the pressure is increased to 230 000 Pa, what will be the new length of the air column? (4)
(ii) If the air column is seen to have a length of 25.4 cm, what will the pressure on the gas be? (4)
(iii) If the pressure was increased to 317 000 Pa, what will be the new length of the air column? (4)
5. In a bicycle pump the original volume of air in the cylinder is 400 cm3. The air is originally at normal atmospheric pressure (100 000 Pa). The handle is pushed in until the volume is only 250 cm3. What is the pressure of the compressed air as it heads into the tyre? (3)
6. Some Oxygen at 1 atmosphere pressure is compressed to 5 atmospheres pressure and then put into a 0.3 m3 cylinder. What was the original volume of the Oxygen before it was compressed? (4)
7. Invent a numerical problem of your own on Boyle's law. Write out the question and your solution. (5)
8. In a bicycle pump the original volume of air in the cylinder is 400 cm3 at 1 atm.. The handle is now pushed in until the volume is only 250 cm3. What is the new pressure of the air? (Assume that the temperature of the air stays constant) (4)
9. A column of air is enclosed in a tube beneath a column of mercury 3 cm long. The tube is held vertically. If the column of air was originally 5 cm long, how long wil it be when 3 cm more mercury is added to the column above the air? (The pressure of the atmosphere is equivalent to a column of mercury 76 cm high) (6)
10. A cylinder of Hydrogen contains 100 litres of gas compressed to 6.2 Atmospheres pressure. How much volume would the original gas have occupied at 1.1 Atmospheres pressure, before it was compressed? (4)
I have downloaded those questions from the web but I have no idea from which site I got them.
