Question

What volume will 1.27 moles of helium gas occupy at STP?

Answer 1

One mole of a gas occupies 22.4 L at STP.

1.27 mol He x (22.4 L / 1 mol) = 28.4 L

You could also use the ideal gas law.

PV = nRT

V = nRT / P = (1.27 mol x 0.08206 L atm / K mol x 273 K) / (1.00 atm)

= 28.4 L

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hope it helps you