Problem: The zinc in a copper-plated penny will dissolve in hydrochloric acid if the copper coating is filed down in several spots (so that the hydrochloric acid can get to the zinc). The reaction between the acid and the zinc is: 2H+ (aq) + Zn (s) → H2 (g) + Zn2+ (aq) When the zinc in a certain penny dissolves, the total volume of gas collected over water at 25 o C was 0.955 L at a total pressure of 750 mm Hg.What mass of hydrogen gas was collected?

FREE Expert Solution

Dalton’s Law states that the total pressure inside a container is obtained by adding all the partial pressures of each non-reacting gas

  • vapor pressure of water @ 25°C = 23.78 mm Hg


Ptotal=PGas 1+PGas 2+PGas 3...Ptotal=PH2+Pwater750 mm Hg=PH2+23.78 mm Hg

PH2=726.22 mm Hg


Ideal gas equation: moles H2


PVRT=nRTRTn=PVRT


mass = moles x molar mass 

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Problem Details

The zinc in a copper-plated penny will dissolve in hydrochloric acid if the copper coating is filed down in several spots (so that the hydrochloric acid can get to the zinc). The reaction between the acid and the zinc is: 

2H+ (aq) + Zn (s) → H2 (g) + Zn2+ (aq) 


When the zinc in a certain penny dissolves, the total volume of gas collected over water at 25 o C was 0.955 L at a total pressure of 750 mm Hg.

What mass of hydrogen gas was collected?

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