For hydrogen molecule, how many mols of it are there in "33.4 L" at STP?

2 Answers
Victoria E.
Feb 9, 2018

At STP, all gases have a molar volume of 22.4 L/mol
(33.4 L)((1mol)/(22.4 L))= 1.49 mol

Truong-Son N.
Feb 9, 2018

I got "1.47 mols"....

If we ASSUME (!!!!) that hydrogen gas is an ideal gas, then we ASSUME that the ideal gas law works:

PV = nRT

  • P is pressure in "atm" or "bar"...
  • V is volume in "L".
  • R = "0.083145 L"cdot"bar/mol"cdot"K" = "0.082057 L"cdot"atm/mol"cdot"K" is the universal gas constant.
  • T is the temperature in "K".
  • n is obviously the mols of IDEAL gas.

And so,

n = (PV)/(RT)

STP is defined since 1982 as 0^@ "C" and "1 bar". STP is defined before 1982 as 0^@ "C" and "1 atm".

Before 1982,

n = ("1 atm"cdot"33.4 L")/("0.082057 L"cdot"atm/mol"cdot"K" cdot "273.15 K")

= "1.49 mols"

But since we're not old-timers who are stuck in the past, we look at AFTER 1982 to obtain:

n = ("1 bar" cdot "33.4 L")/("0.083145 L"cdot"bar/mol"cdot"K" cdot "273.15 K")

= ulcolor(blue)"1.47 mols"

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