Question

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Calculate the work done (in joules) when 47.1 g of tin dissolves in excess acid at 1.04 atm and 22°C. Assume ideal gas behavior.

Sn(s) + 2H+(aq) → Sn2+(aq) + H2(g)

Answer 1

Work done in a chemical reaction

Change in volume = final volume - initial volume

Volume change in primarily due to the formation of H2(g)

Therefore,

by ideal gas behaviour,

work done = P(final volume - initial volume)

                 = P x volume occupied by H2 gas

We know,

PV = nRT

or,

V = nRT/P

feeding this in above relation,

work done = nRT

with,

n = moles of Sn = 47.1 g/118.71 g/mol = 0.40 mol

R = gas constant = 8.314 J/K.mol

T = 22 oC + 273 = 295 K

So,

work done = 0.40 x 8.314 x 295

                  = 981.052 J