Cheat Sheet: 60-Second NEET Thermodynamics Review

MUST-KNOW EQUATIONS

$\Delta U = q + w \qquad \Delta H = \Delta U + \Delta n_g RT$

$\Delta G = \Delta H - T\Delta S \qquad \Delta G^\circ = -RT\ln K$

$w_{rev} = -nRT\ln\frac{V_2}{V_1} \qquad w_{irrev} = -P_{ext}\Delta V \qquad w_{free} = 0$

$C_p - C_v = R \qquad \Delta S = q_{rev}/T$

MUST-KNOW FACTS

Item	Value/Rule
$\Delta G$ at equilibrium	$= 0$ (NOT $\Delta G^\circ$ )
$\Delta H_f^\circ$ of any element	$= 0$
Combustion enthalpy sign	Always $-$
Atomization/ionization sign	Always $+$
Lattice/hydration enthalpy	Always $-$
$\Delta n_g$ rule	Gas moles only
IUPAC work sign	ON system = $+$

SPONTANEITY TABLE

$\Delta H$	$\Delta S$	Spontaneous when
$-$	$+$	Always
$+$	$-$	Never
$-$	$-$	Low T (below $\Delta H/\Delta S$ )
$+$	$+$	High T (above $\Delta H/\Delta S$ )

HEAT CAPACITIES (per mole)

Gas	$C_v$	$C_p$	$\gamma$
Mono	$\frac{3R}{2}$	$\frac{5R}{2}$	$\frac{5}{3}$
Di	$\frac{5R}{2}$	$\frac{7R}{2}$	$\frac{7}{5}$

PROCESS ZERO QUANTITIES

Isothermal ideal gas: $\Delta U = 0$ , $\Delta H = 0$
Adiabatic: $q = 0$
Isochoric: $w = 0$
Free expansion: $w = 0$ , $q = 0$ , $\Delta U = 0$
Cyclic: $\Delta U = 0$ , $\Delta H = 0$

MNEMONIC BUNDLE

"Exo-Plus Always, Endo-Minus Never" (spontaneity) "W-ON positive, Q-IN positive" (IUPAC signs) "3-5-7 for 1-2-3 atoms, add R for Cp" (heat capacities) "BIG K → Negative G" (K and $\Delta G^\circ$ relation)