8. a volume of 7.5 l of hydrogen gas at stp was produced from the single-replacement
reaction of zinc with nitric acid. calculate the mass of zinc needed for this reaction.

20.60 g

Explanation:

We are given;

Volume of hydrogen gas produced at STP as 7.5 L

Required to determine the mass of zinc needed for the reaction.

We are going to first write the equation for the reaction;

Zn(s) + 2HNO₃(aq) → Zn(NOₐ)₂ + H₂(g)

Now, we determine the number of moles of Hydrogen gas.

we know that 1 mole of a gas occupies 22.4 L at STP

Therefore;

Moles of Hydrogen = 7.05 L ÷ 22.4 L/mol

                                 = 0.315 moles

Then, we determine the number of moles of Zinc that reacted

From the reaction 1 mole of zinc reacts to produce 1 mole of hydrogen.

Therefore,

Moles of Zinc = Moles of Hydrogen

Thus, moles of zinc = 0.315 moles But, molar mass of zinc is 65.38 g/mol

Hence;

Mass of Zinc = 0.315 moles × 65.38 g/mol

                     = 20.60 g

Thus, the mass of zinc that reacted 20.60 g

Iwould you figure it out but you don't have a picture or in your question as to what the physical property you're looking for is

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