# Problem: Modern pennies are composed of zinc coated with copper. A student determines the mass of a penny to be 2.482 g and then makes several scratches in the copper coaling (to expose the underlying zinc). 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) + 2 HCl(aq) → H2(g) + ZnCl(aq)The student collects the hydrogen produced over water at 25 °C. The collected gas occupies a volume of 0.899 L at a total pressure of 791 mmHg. Calculate the percent zinc (by mass) in the penny. (Assume that all the Zn in the penny dissolves.)

🤓 Based on our data, we think this question is relevant for Professor Morkowchuk's class at UVA.

###### Problem Details

Modern pennies are composed of zinc coated with copper. A student determines the mass of a penny to be 2.482 g and then makes several scratches in the copper coaling (to expose the underlying zinc). 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) + 2 HCl(aq) → H2(g) + ZnCl(aq)

The student collects the hydrogen produced over water at 25 °C. The collected gas occupies a volume of 0.899 L at a total pressure of 791 mmHg. Calculate the percent zinc (by mass) in the penny. (Assume that all the Zn in the penny dissolves.)

What scientific concept do you need to know in order to solve this problem?

Our tutors have indicated that to solve this problem you will need to apply the Collecting Gas Over Water concept. If you need more Collecting Gas Over Water practice, you can also practice Collecting Gas Over Water practice problems.

What is the difficulty of this problem?

Our tutors rated the difficulty ofModern pennies are composed of zinc coated with copper. A st...as high difficulty.

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Our expert Chemistry tutor, Jules took 6 minutes and 43 seconds to solve this problem. You can follow their steps in the video explanation above.

What professor is this problem relevant for?

Based on our data, we think this problem is relevant for Professor Morkowchuk's class at UVA.

What textbook is this problem found in?

Our data indicates that this problem or a close variation was asked in Chemistry: A Molecular Approach - Tro 2nd Edition. You can also practice Chemistry: A Molecular Approach - Tro 2nd Edition practice problems.