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?

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Answer 1 · 2016-10-13T04:22:00

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

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