The number of liters of gas that would be produced at stp is calculated as follows
by use of ideal gas equation calculate the number of moles used
that is Pv=nRT where n is number of moles
n= Pv/RT
P=5100 mm hg
R=62.36 mm hg
T = 29+273= 302 K
V=20.1 L
n=(5100 x 20.1)/( 62.36 x 302) = 5.4 moles
at STP 1 mole = 22.4 L, what about 5.4 moles
= 5.44 mole/1mole x 22.4 L = 120 L(answer C)