Find the mass of #"2.0 L"# of helium gas at STP? The molar mass is #"4.002602 g/mol"#.

Question

Ellie Andrews · Accepted Answer

Given that we are at STP, we can solve this problem using the ideal gas law:

#PbarV = RT#

where #barV = V/n#, the molar volume.

At STP, for an ideal gas:

We can solve for the ideal molar volume #barV_"ideal"#, and then from that determine the #"mol"#s of helium and thus the mass.

#barV_"ideal" = (RT)/P#

#= (0.083145*273.15)/(1) = color(green)"22.711 L/mol"#

Consequently, we are aware that, assuming helium is perfect:

#barV_"ideal" = barV_"He"#

#"22.711 L"/"1 mol ideal gas" = "2.0 L"/(n_"He")#

#n_"He" = "0.0881 mol"#

Finally, translating to grams:

#0.0881 cancel"mol He" xx ("4.002602 g")/(cancel"mol He")#

#color(blue)("= 0.3525 g He")#

Owen Ambrose · Answer

The mass of helium present is #"0.36 g"#.

"STP" is defined as "273.15 K" and "1 atm". The mass of helium in grams can be calculated by multiplying the moles of helium by its molar mass, which can be found using the ideal gas law. ideal gas law #PV=nRT#, where #P# is pressure, #V# is volume, #n# is moles, #R# is the gas constant, a #T# is the temperature. Known/Given #P="1 atm"# #V="2.0 L"# #R="0.08206 L atm K"^(-1) "mol"^(-1)"# #T="273.15 K"# Molar mass of helium: #"4.002602 g/mol"# Unknown Moles of helium:#n_"He"# Mass of helium in grams Formulas #PV=nRT# #n_"He"xx(4.002602"g He")/(1"mol He")# Resolution Rearrange the ideal gas law equation to isolate #n#, then solve. #n=(PV)/(RT)# #n=(1cancel"atm"*2.0cancel"L")/(0.08206cancel"L atm K"^(-1)"mol"^(-1)*273.15cancel"K")="0.089 mol He"# #0.089cancel"mol He"xx(4.002602"g He")/(1cancel"mol He")="0.36 g He"#

Serenity Allen · Answer

undefined To find the mass of 2.0 L of helium gas at STP (Standard Temperature and Pressure), we first need to determine the number of moles of helium using the ideal gas law equation:

n = (PV) / (RT)

Where:
P = pressure (STP pressure is 1 atm)
V = volume (2.0 L)
R = ideal gas constant (0.0821 L·atm/mol·K)
T = temperature (STP temperature is 273.15 K)

Once we find the number of moles (n), we can use the molar mass of helium (4.002602 g/mol) to calculate the mass:

mass = n × molar mass

Substituting the values into the equations, we get:

n = (1 atm × 2.0 L) / (0.0821 L·atm/mol·K × 273.15 K)
n ≈ 0.0810 mol

mass ≈ 0.0810 mol × 4.002602 g/mol ≈ 0.324 g

Therefore, the mass of 2.0 L of helium gas at STP is approximately 0.324 grams.