Question

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A sample of zinc metal is allowed to react completely with an excess of hydrochloric acid:

Zn(s) + 2 HCl(aq) → ZnCl2(aq) + H2(g)

The hydrogen gas produced is collected over water at 25.0°C. The volume of the gas is 8.45 L, and the atmospheric pressure is 0.951 atm. Calculate the amount of zinc metal in grams consumed in the reaction.

(Vapor pressure of water at 25°C = 23.8 mmHg.)

ANSWER ____ g Zn

Answer 1

Zn(s) + 2 HCl(aq) → ZnCl2(aq) + H2(g)

total pressure (PT)   = 0.951atm

vapr pressure of water at 25⁰C ( PH2O) = 23.8/760 = 0.0313atm

pressure of H2 (PH2) = PT - PH2O

                                   = 0.951-0.0313

                                    = 0.9197atm

V   = 8.45L

T   = 25+273 = 298K

PV = nRT

n = PV/RT

     = 0.9197*8.45/0.0821*298

      = 0.3176moles

Zn(s) + 2 HCl(aq) → ZnCl2(aq) + H2(g)

1 mole of H2 produced from 1 mole of Zn react with HCl

0.3176 moles of H2 produced from 0.3176 moles of Zn react with HCl

mass of Zn = no of moles * gram molar mass

                    = 0.3176*65.4 = 20.77g of Zn >>>>answer