After starting with 0.343 g Al and excess HCl, the volume if H2 gas collected ov

Question

After starting with 0.343 g Al and excess HCl, the volume if H2 gas collected over water was 472 mL. The atmospheric pressure was 754 mmHg and the temperature was 21 degrees Celsius. How many moles of H2 were produced by this reaction? Calculate the experimental molar mass of Al. What is the percent error for the experimental molar mass? Lisa S.
After starting with 0.343 g Al and excess HCl, the volume if H2 gas collected over water was 472 mL. The atmospheric pressure was 754 mmHg and the temperature was 21 degrees Celsius. How many moles of H2 were produced by this reaction? Calculate the experimental molar mass of Al. What is the percent error for the experimental molar mass? Lisa S.
Lisa S.

Explanation / Answer

Pv=nrt

1 atm = 760mmHg, so 754/760=0.992 atm=p

T=21+273=294K

V=0.472L

(0.992)*0.472=n0.08206*294

Moles of H2 = 0.019 moles

For 3moles oh H2, 2 moles of Al required

Mass of Al = 0.019*2/3=0.0129 * mw of Al which is equal to initial mass of Al

So mw of Al = 0.343/0.0129=26.58

Theoretical molecular weight of Al is 26.98

%error = 26.98-26.58/26.98 *100= 39%

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