Question

Which one of the following reactions would you expect to have a change in the standard entropy with a small magnitude? 4/2CH2(g) + O2(6) -- 1/20026)+H2013) C2H6lg)+7/20218) -- 2002(8) + 3H2O(g) c C2H2(g) + 5/20218) -- 200268) + H2O(g) 2C2H668) + 702(8) -- 400268) + 6H2O(g)

Answer 1

$\bigtriangleup n_g=$Sum of number of mole of product in gaseous state -Sum of number of mole of product in gaseous state

$\bigtriangleup n_g=\sum n_p(g)-\sum n_r(g)$

Higher the value of , higher will be the entropy.

If is positive , entropy increase

If =0 , no entropy increase or decrease

If is negative , entropy will decrease

A)

Δημ = 1/2 +1 – 1 – 1/2 = 0

No entropy increase

B)

$\bigtriangleup n_g=2+3-1-7/2=0.5$

Entropy will increase

C)

$\bigtriangleup n_g=2+1-1-5/2=-0.5$

Entropy will decrease

D)

$\bigtriangleup n_g=4+6-7-2=1$

Entropy will increase.

In (B) and (D) entropy will increase , but in (B) there will be change in entropy with small magnitude.