Rate-determining stepIn chemical kinetics, the overall rate of a reaction is often approximately determined by the slowest step, known as the rate-determining step (RDS or RD-step or r/d step) or rate-limiting step. For a given reaction mechanism, the prediction of the corresponding rate equation (for comparison with the experimental rate law) is often simplified by using this approximation of the rate-determining step. In principle, the time evolution of the reactant and product concentrations can be determined from the set of simultaneous rate equations for the individual steps of the mechanism, one for each step.
ExpenseAn expense is an item requiring an outflow of money, or any form of fortune in general, to another person or group as payment for an item, service, or other category of costs. For a tenant, rent is an expense. For students or parents, tuition is an expense. Buying food, clothing, furniture, or an automobile is often referred to as an expense. An expense is a cost that is "paid" or "remitted", usually in exchange for something of value. Something that seems to cost a great deal is "expensive".
2-8-2Under the Whyte notation for the classification of steam locomotives, 2-8-2 represents the wheel arrangement of two leading wheels on one axle, usually in a leading truck, eight powered and coupled driving wheels on four axles and two trailing wheels on one axle, usually in a trailing truck. This configuration of steam locomotive is most often referred to as a Mikado, frequently shortened to Mike. It was also at times referred to on some railroads in the United States as the McAdoo Mikado and, during World War II, the MacArthur.
