Umwandlungsgrad

Umwandlungsgrad is a dimensionless quantity used in chemistry and related fields to quantify the fraction of a reactant that has been converted to products in a chemical reaction. It is commonly denoted X_A for a reactant A and ranges from 0 (no conversion) to 1 (complete conversion). In practice it is often expressed as a percentage.

For a reaction a A → products with initial amount n_A0, the amount of A at time t is n_A = n_A0 − a ξ, where ξ is the extent of reaction. The degree of conversion is X_A = (n_A0 − n_A)/n_A0 = a ξ/n_A0. In mass terms, X_A = (m_A0 − m_A)/m_A0. The conversion applies to each reactant; the maximum is set by the limiting reagent.

In batch reactors, X_A increases with time according to kinetics. In continuous-flow reactors, X_A depends on residence time τ and operating conditions such as temperature, pressure and catalysts. Conversion is a key performance indicator, often considered together with selectivity and yield.

Outside chemistry, Umwandlungsgrad is also used to describe the efficiency of converting one form of energy or signal into another, for example solar-to-electric energy or chemical-to-electrical energy in a fuel cell.

Limitations include multi-component systems where each species has its own conversion, back-reactions that reduce X_A, and measurement uncertainties. The concept is central to reactor design, catalysis and process optimization.