Which of the following relation is not correct?

🧠 The sign in $\Delta H = \Delta U + P\Delta V$ is plus, not minus Option (a) writes a minus sign — that makes it wrong. The correct form is: $\Delta H = \Delta U + P\Delta V$

The other options are all standard results: (b) $\Delta U = q + w$ — First Law ✓ (c) $\Delta S_{\text{sys}} + \Delta S_{\text{surr}} \geq 0$ — Second Law ✓ (d) $\Delta G = \Delta H - T\Delta S$ — Gibbs energy definition ✓

⚠️ Don't confuse $\Delta H = \Delta U + P\Delta V$ with the rearranged form $\Delta U = \Delta H - P\Delta V$. Both are valid — only the wrong sign in (a) makes it incorrect.

$\boxed{\text{Answer: (a)}}$