Modern pennies are composed of zinc coated with copper. A student determines the mass of a...

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Chemistry

Modern pennies are composed of zinc coated with copper. Astudent determines the mass of a penny to be 2.480 g and then makesseveral scratches in the copper coating (to expose the underlyingzinc). The student puts the scratched penny in hydrochloric acid,where the following reaction occurs between the zinc and the HCl(the copper remains undissolved):
Zn(s)+2HCl(aq)→H2(g)+ZnCl2(aq)
The student collects the hydrogen produced over water at 25 ∘C. Thecollected gas occupies a volume of 0.903 L at a total pressure of786 mmHg .

Calculate the percent zinc in the penny. (Assume thatall the Zn in the penny dissolves.)

Answer & Explanation Solved by verified expert
4.3 Ratings (832 Votes)
Solution Given data Mass of penny 2480 g Volume of H2 gas collected 0903 L Temperature 25 C 273 298 K Total pressure 786 mmHg At 25 C vapor pressure of water 238 mmHg Therefore the pressure of the H2 gas total pressure vapor    See Answer
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