Everything Science Grade 11

5.5 CHAPTER 5. THERMAL PROPERTIES AND IDEAL GASES

Example 6: General Gas Equation 2

QUESTION

A cylinder that containsmethane gas is kept at atemperature of 15◦C and exerts a pressureof

7 atm. If the temperature of the cylinder increases to 25◦C, what pressure does the gas now

exert? (Refer to Table 5.1 to see what an ’atm’ is.

SOLUTION

Step 1 : Write down all the information that you knowabout the gas.

p 1 = 7 atm and p 2 =?

T 1 = 15◦C and T 2 = 25◦C

Step 2 : Convert the known values to SI units if necessary.

Here, temperature mustbe converted into Kelvin, therefore:

T 1 = 15 + 273 = 288 K

T 2 = 25 + 273 = 298 K

Step 3 : Choose a relevant gas law equation that will allow you to calculate theunknown

variable.

Since the volume of thecylinder is constant, wecan write:

p 1

T 1

=

p 2

T 2

Therefore,

p 2 =

p 1 × T 2

T 1

Step 4 : Substitute the known values into the equation.Calculate the unknownvariable.

p 2 =

7 atm× 298 K

288 K

= 7. 24 atm

The pressure of the gasis 7.24 atm.

Example 7: General Gas Equation 3

QUESTION

A gas container can withstand a pressure of 130 kPa before it will explode. Assuming that

the volume of the gas inthe container stays the same, at what temperature will the container