Question

Based on some experimental data each of the following equations represents a reaction in which the change in entropy, $\Delta$ S, is positive EXCEPT.

• A. $CaC{O}_3\left(s\right)\to CaO\left(s\right)+C{O}_2\left(g\right)$
• B. $Zn\left(s\right)+2H^{+}\left(aq\right)\to H_2\left(g\right)+Z{n}^{2+}\left(aq\right)$
• C. $2C_2{H}_6\left(g\right)+7O_2\left(g\right)\to 4C{O}_2\left(g\right)+6H_{2}O\left(g\right)$
• D. $NaCl\left(s\right)\to N{a}^{+}\left(aq\right)+C{l}^{-}\left(aq\right)$
• E. $N_2\left(g\right)+3H_2\left(g\right)\to 2N{H}_3\left(g\right)$

Answer 1

The correct option is E $N_2\left(g\right)+3H_2\left(g\right)\to 2N{H}_3\left(g\right)$

$A)$ 1 mole of solid changes to 1 mole of solid and 1 mole of gas

Small number of molecules becomes large number of molecules then entropy increases. Also, due to formation of gas entropy increases.

$B)$ 1 mole of solid and 2 moles of aqueous changes to 1 mole of gas and 1 mole of aqueous.

Due to formation of gas entropy increases

$C)$ 9 moles of gas changes to 10 moles of gas

Due to formation of large number of molecules in the product than reactant entropy increases.

$D)$ 1 mole of solid changes to 2 moles of aqueous

Due to formation of higher number of molecules in product and formation of aqueous from solid, entropy increases

$E)$ 4 moles of gas changes to 2 moles of gas

Due to small number of molecules in the product side than the reactant, entropy decreases.