A gas has a volume of 435 mL at #25^@"C"# and #"98.7 kPa"#. What would the volume of the gas be at STP?

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Answer 1 · 2014-11-22T20:01:16

The new volume would be #"394 mL"#.

This problem can be solved using the combined gas law with the equation:

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

The temperature scale used in the gas laws is the Kelvin scale, so the Celsius temperatures will need to be converted to Kelvins.

STP for the gas laws are #"273.15 K"# and #"100 kPa"#.

Given/Known:

#V_1= "435mL"#

#T_1 = "25"^o"C" + "273.15" = "298K"#

#P_1 = "98.7 kPa"#

#T_2 = "273.15K"#

#P_2 = "100 kPa"#

Unknown:

#"V"_2#

Solution:

Rearrange the formula to isolate #V_2#. Plug in the known values and solve.

#"V"_2 = (V"_1P_1T_2)/(P_2T_1)#

#V_2 = ((435"mL")xx(98.7"kPa")xx(273.15"K"))/((100"kPa")xx(298"K")) = "394mL"# (rounded to three significant figures)