20.60 g
We are given;
Required to determine the mass of zinc needed for the reaction.
Zn(s) + 2HNO₃(aq) → Zn(NOₐ)₂ + H₂(g)
we know that 1 mole of a gas occupies 22.4 L at STP
Moles of Hydrogen = 7.05 L ÷ 22.4 L/mol
= 0.315 moles
Then, we determine the number of moles of Zinc that reacted
Therefore,
Moles of Zinc = Moles of Hydrogen
Hence;
Mass of Zinc = 0.315 moles × 65.38 g/mol
= 20.60 g
Thus, the mass of zinc that reacted 20.60 g