IUPAC > Gold Book > alphabetical index > R > rate of formation, v n , y or v c , y


rate of formation, v n , y or v c , y

Like the rate of consumption, the rate of formation of a specified product may be defined in two ways:
  1. As the time derivative of the amount of a product. Thus for a product Y, present at any time in amount n Y. the rate of its formation may be given by:
    v n Y = d n Y d t
    This definition is particularly appropriate for open systems.
  2. For kinetics in closed systems it is more usual to define a rate of formation per unit volume, denoted v c Y:
    v c Y = 1 V d n Y d t
    When the volume is constant this reduces to:
    v c Y = 1 V d n Y d t = d Y d t
    When the volume is not constant the relationship n Y = Y V may be differentiated to give:
    d n Y = V d Y + Y d V
    and the rate of formation becomes:
    v c Y = d Y d t + Y V d V d t
    A rate of formation may be specified even for a reaction of time dependent stoichiometry or of unknown stoichiometry.
PAC, 1996, 68, 149 (A glossary of terms used in chemical kinetics, including reaction dynamics (IUPAC Recommendations 1996)) on page 181
Interactive Link Maps
First LevelSecond LevelThird Level
Cite as:
IUPAC. Compendium of Chemical Terminology, 2nd ed. (the "Gold Book"). Compiled by A. D. McNaught and A. Wilkinson. Blackwell Scientific Publications, Oxford (1997). XML on-line corrected version: http://goldbook.iupac.org (2006-) created by M. Nic, J. Jirat, B. Kosata; updates compiled by A. Jenkins. ISBN 0-9678550-9-8. doi:10.1351/goldbook.
Last update: 2014-02-24; version: 2.3.3.
DOI of this term: doi:10.1351/goldbook.R05152.
Original PDF version: http://www.iupac.org/goldbook/R05152.pdf. The PDF version is out of date and is provided for reference purposes only. For some entries, the PDF version may be unavailable.
Current PDF version | Version for print | History of this term