Question

The volume of a gas is 27.5 mL at 22°C and 740 mmHg. What will be its volume at 15.0°C and 755 mmHg?

Answer 1

The new volume will be `~~26 "mL"` rounded to two significant figures.

Explanation:

This question involves the combined gas law. The equation to use is:

When working with gas laws, the temperature is always in Kelvins. To get Kelvins from a Celsius temperature, add 273.15 to the Celsius temperature.

Determine what is known and what is unknown.

Known
`P_1="740 mmHg"`
`V_1="27.5 mL"`
`T_1="22"^@"C"+"273.15"="295 K"`
`P_2="755 mmHg"`
`T_2="15.0"^@"C"+"273.15"="288 K"`

Unknown
`V_2`

Solution
Rearrange the equation to isolate `V_2`. Substitute the known values into the equation and solve.

`(P_1V_1)/T_1=(P_2V_2)/T_2`

`V_2=(P_1V_1T_2)/(T_1P_2)`

`V_2=(740"mmHg"xx27.5"mL"xx288"K")/(295"K"xx755"mmHg")` `=` `~~26 "mL"` rounded to two significant figures