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The Van 't Hoff equation relates the change in the equilibrium constant, K eq, of a chemical reaction to the change in temperature, T, given the standard enthalpy change, Δ r H ⊖, for the process.
The standard enthalpy of reaction (denoted ) for a chemical reaction is the difference between total product and total reactant molar enthalpies, calculated for substances in their standard states.
Hellin's law, also called Hellin-Zeleny's law, is an empirical observation in demography that the approximate rate of multiple births is one n-tuple birth per 89 n-1 singleton births: twin births occur about once per 89 singleton births, triplets about once per 89 2, quadruplets about once per 89 3, and so on.
For example, a pregnant female who carried one pregnancy to term with a surviving infant; carried one pregnancy to 35 weeks with surviving twins; carried one pregnancy to 9 weeks as an ectopic (tubal) pregnancy; and has three living children would have a TPAL annotation of T1, P1, A1, L3. This could also be written as 1-1-1-3.
For many substances, the formation reaction may be considered as the sum of a number of simpler reactions, either real or fictitious. The enthalpy of reaction can then be analyzed by applying Hess' law, which states that the sum of the enthalpy changes for a number of individual reaction steps equals the enthalpy change of the overall reaction.
A median of 288 days (274 days from the date of ovulation) for first-time mothers and 283 days (269 days from the date of ovulation) for mothers with at least one previous pregnancy was found by a 1990 study of 114 white, private-care patients with uncomplicated pregnancies and spontaneous labor. The authors suggest that excluding pregnancies ...
Montevideo units are a method of measuring uterine performance during labor.They were created in 1949 by two physicians, Roberto Caldeyro-Barcia and Hermogenes Alvarez, from Montevideo, Uruguay.
In physical chemistry, the Arrhenius equation is a formula for the temperature dependence of reaction rates.The equation was proposed by Svante Arrhenius in 1889, based on the work of Dutch chemist Jacobus Henricus van 't Hoff who had noted in 1884 that the van 't Hoff equation for the temperature dependence of equilibrium constants suggests such a formula for the rates of both forward and ...