McKnecht CH5 Exercise 5.69 Exercise 5.69 Part A The zinc in a copper-plated penn

Question

McKnecht CH5 Exercise 5.69 Exercise 5.69 Part A 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 C was 0.951 L at a total pressure of 742 mm Hg What mass of hydrogen gas was collected? m= 10.076 ] Incorrect; One attempt remaining; Try Again

Explanation / Answer

A)

Mass of gas

PV = nRT

n = PV/(RT)

Ptotal = Pgas + Pvapor

Pgas = Ptotal - Pvapor = 742 - 23.8 = 718.2 mm Hg

V = 0.951 L;

T = 25°C = 298K

substitute

n = (718.2)(0.951)/(62.4*298)

n = 0.03673 mol o fH2

mass = mol*MW = 0.03673*2 = 0.07346 g

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