Lesson-specific diagram for Gas-volume stoichiometry. It visualizes the reasoning sequence tied to $V\leftrightarrow n\xrightarrow{\nu_B/\nu_A}n\leftrightarrow V$. Text alternative: Gas-volume calculations must state conditions and avoid mixing incompatible molar-volume assumptions. Choose a representation that matches the chemical scale and evidence; do not infer more precision or mechanism than the data support.