which reaction results in a negative δs? 2hgo(s)→2hg(l) + o₂(g) nacl(s)→na⁺(aq) + cl⁻(aq) h₂o(l)→h₂o(s)

To determine which reaction has a negative (\Delta S) (entropy change), we analyze the change in disorder (entropy) for each reaction:

Reaction 1: (2\text{HgO}(s) \rightarrow 2\text{Hg}(l) + \text{O}_2(g))

• Explanation: A solid (low entropy) is converted into a liquid and a gas (both higher entropy than solid). The production of a gas increases disorder. So, (\Delta S) is positive (entropy increases).

Reaction 2: (\text{NaCl}(s) \rightarrow \text{Na}^+(aq) + \text{Cl}^-(aq))

• Explanation: A solid (ordered structure) is dissolved into ions in solution. Dissolving a solid into ions increases the number of particles and their freedom of movement, so disorder (entropy) increases. Thus, (\Delta S) is positive.

Reaction 3: (\text{H}_2\text{O}(l) \rightarrow \text{H}_2\text{O}(s))

• Explanation: A liquid (higher entropy than solid) is converted into a solid (lower entropy, more ordered structure). The system becomes more ordered, so disorder (entropy) decreases. Thus, (\Delta S) is negative.

The reaction with a negative (\Delta S) is (\boldsymbol{\text{H}_2\text{O}(l) \rightarrow \text{H}_2\text{O}(s)}).