Homework Help: chemistry

Posted by joann on Monday, December 3, 2012 at 9:58pm.

A 0.286g sample of Zn was used to produce H2(g)by the reaction.
Zn(s)+ 2HCl(aq)> ZnCl2(aq) + H2(g)

The barometric pressure was recorded as 761.6mm Hg and room temperature was 20degreesC. When the water levels of the eudiometer tube and graduated cylinder were equal, the volume of H2 was measured as 94.8mL. Calculate the number of moles of hydrogen gas produced in the reaction. Also, calculate the theoretical number of moles that can be obtained with the given amount of metal. (assume the acid is in excess) Finally, determine the error

chemistry - DrBob222, Tuesday, December 4, 2012 at 12:16am
1. Use PV = nRT and solve for n = number of mols H2.
P = (761.8- vapor pressure H2O @ 20C)/760 = atm.
V = 0.0948 L
R = 0.08206 L*atm/mol*K
T = 273 + 20 = ?

2.mols Zn = grams/molar mass
Convert mols Zn to mols H2 using the coefficients in the balanced equation. That's mols H2 = mols Zn = theoretical mols H2 produced.

3. T = theoretical value.
E = experimental value.
%error = [(E-T)/T]*100

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