Average and instantaneous rate of a reactionअभिक्रिया का औसत और तात्क्षणिक वेगAverage and instantaneous rate of a reaction

NCERT Fig 3.1 · Class 12 Chemistry · Chapter 3 · interactive diagram

Parts and what they mean

• [R] vs time — reactant concentration decreases ([R] बनाम समय — अभिकारक की सांद्रता घटती है) — The curve is steep at first and flattens later: the rate falls as R is used up.
• [P] vs time — product concentration increases ([P] बनाम समय — उत्पाद की सांद्रता बढ़ती है) — Rate of appearance of P = +Δ[P]/Δt.
• Average rate = −Δ[R]/Δt (slope of the chord) (औसत वेग = −Δ[R]/Δt (जीवा की ढलान)) — Depends on the time interval chosen; it cannot give the rate at one particular instant.
• Instantaneous rate = −d[R]/dt (slope of the tangent) (तात्क्षणिक वेग = −d[R]/dt (स्पर्श रेखा की ढलान)) — Average rate over a very small interval (Δt → 0). Found by drawing a tangent at time t.
• Tangent on [P] curve: rate = +d[P]/dt ([P] वक्र पर स्पर्श रेखा: वेग = +d[P]/dt) — For R → P (1 : 1), −d[R]/dt = +d[P]/dt at every instant.
• Δt = t2 − t1 (time interval) (Δt = t2 − t1 (समय अंतराल)) — Units: s, min or h.
• Δ[R] = [R]2 − [R]1 (negative) (Δ[R] = [R]2 − [R]1 (ऋणात्मक)) — Negative because R decreases, so a minus sign makes the rate positive.
• Axes: concentration (mol L⁻¹) vs time (अक्ष: सांद्रता (mol L⁻¹) बनाम समय) — Rate unit = concentration time⁻¹, e.g. mol L⁻¹ s⁻¹.

Original diagram drawn by Simple Learning Hub, based on NCERT Fig 3.1. Report a mistake