A piece of zinc (Zn) is allowed to react with an excess quantity of sulfuric aci

Question

A piece of zinc (Zn) is allowed to react with an excess quantity of sulfuric acid, and the hydrogen gas produced is collected in a gas buret by displacement of water. This is similar to the molar volume of oxygen lab you did. a) Write a balanced chemical equation for this reaction. The other product is aqueous zinc sulfate. Include physical state of all substances. b) Ignoring the effect of water vapor on the system, calculate the grams of zinc needed to produce 92.00 mL of hydrogen gas at 24.6 deg C and 739 torr pressure.

Explanation / Answer

Solution :-

a). Balanced reaction equation

Zn(s) + H2SO4(aq)   ------- > ZnSO4(aq) + H2(g)

b). temperature = 24.6 C +273 = 297.6 K

pressure = 739 torr * 1atm / 760 torr = 0.97237 atm

volume = 92.00 ml * 1 L / 1000 ml = 0.0920 L

now lets calculate moles of H2

PV= nRT

PV/RT = n

0.97237 atm * 0.0920 L / 0.08206 L atm per mol K * 297.6 K = n

0.003663 mol H 2 = n

Now using the mole ratio lets calculate the moles of Zn

0.003663 mol H2 * 1 mol Zn / 1 mol H2 = 0.003663 mol Zn

Now lets convert moles of Zn to its mass

Mass of Zn = moles * molar mass

                    = 0.003663 mol Zn * 65.39 g per mol

                    = 0.240 g Zn

So the mass of Zn reacted = 0.240 g

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