1/17 Entropy

Which phase of matter has the greatest motion and least orderly arrangement?

• solid
• liquid
• gas

Which phase change represents a decrease in entropy?

• solid to liquid

• gas to liquid

• liquid to gas

• solid to gas

Given the change of phase:

CO₂(g) —> CO₂(s)

As CO₂(g) changes to CO₂(s), the entropy of the system

• decreases

• increases

• remains the same

Entropy of a system increases when a reaction increases the number of particles.

• True

• False

Which of these reactions shows a DECREASE in entropy?

• CaCO₃(s) → CaO(s) + CO₂(g)

• 3O₂(g) → 2O₃(g)

• 2NH₃(g) → 3H₂(g) + N₂(g)

• C₆H₆(l) → C₆H₆(g)

Which reaction has a +ΔS ?

• AgNO₃(aq) + NaCl(aq) → AgCl(s) + NaNO₃(aq)

• H₂O(g) + CO₂(g) → H₂CO₃(aq)

• H₂(g) + I₂(g) → 2Hl(g)

• C₂H₂O₂(g) → 2CO(g) + H₂(g)

Describe the change in entropy for this reaction:

C _(s) + H₂O _(g)  →  CO _(g) + H_2 (g)

• increase in entropy, because the number of particles increases

• decrease in entropy, because the number of particles increases

• decrease in entropy, because gases have higher entropy than solids

• increase in entropy, because gases have higher entropy than solids

Describe the change in entropy for this reaction:

C₂H_4 (g) + H_2 (g)  →  C₂H_6 (g)

• increase in entropy, because the number of particles increases

• decrease in entropy, because the number of particles decreases

• cannot be determined, as there is no change in phases

Describe the change in entropy for this reaction:

CO _(g) + 3 H_{2 (g)} → CH_{4 (g)} + H₂O _(g)

• increase in entropy, because the number of particles increases

• decrease in entropy, because the number of particles decreases

• cannot be determined, as there is no change in phases

Describe the change in entropy for this reaction:

2 O_3 (g)  →  3 O_2 (g)

• increase in entropy, because the number of particles increases

• decrease in entropy, because the number of particles decreases

• cannot be determined, as there is no change in phases