Hey There!
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Answer:

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DATA:
Mass of Helium = 4
Helium = 55 liters
How many moles = ?
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SOLUTION:
By the equation(AT S.T.P) of,
Moles =

Substitute the values,
Moles =

Simplify the fraction,
Moles = 2.5 grams/moles
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Best Regards,
'Borz'