Question

For each of the processes (or reactions) below, a – d, indicate whether it will result in an "increase" or a "decrease" in entropy.

(a) 1 mol H2O (gas, 2 Liter vessel, 300 K) -----> 1 mol H2O (gas, 1 Liter vessel, 300 K)

(b) 1 mol Br2 (liquid, 250 K) -------> 1 mol Br2 (gas, 250 K)

(c) 1 mol Fe (solid, 300 K) -------> 1 mol Fe (solid, 200 K)

(d) SiH4 (g) + 2 O2 (g) -------> SiO2 (s) + 2 H2O (g)

Answer 1

entropy is nothing but a random ness

(a) 1 mol H2O (gas, 2 Liter vessel, 300 K) -----> 1 mol H2O (gas, 1 Liter vessel, 300 K)

here you decrease the randam ness that means entropy decresed

1 mol Br2 (liquid, 250 K) -------> 1 mol Br2 (gas, 250 K)

Br2 liquid become gas that means entropy will increase

(c) 1 mol Fe (solid, 300 K) -------> 1 mol Fe (solid, 200 K)

when you decrease the the temperature molecular motion will decrease so entropy will decrease

(d) SiH4 (g) + 2 O2 (g) -------> SiO2 (s) + 2 H2O (g)

here total three moles of gas molecule become 3 gas

in product one mole of solide and 2 moles of gas so entropy will decrease