In this task you will be given a text passage from a trivia quiz. You should choose the category this question belongs to from these categories: History, Science, Social Science, Fine Arts, Literature. You can only choose one category, so if in doubt, please choose the closest match.

[EX Q]: An approximation of it named for Russell uses the TDS value to determine one of its parameters via the Langelier approximation, while one constant that appears in it has units of moles per kilogram to the one half power, according the Bates-Guggenheim convention. Along with Guggenheim, Scatchard and Bronsted improved upon this model by developing the SIT theory, and that model has a better fit than a modification of it named for Davies. This relationship assumes the existence of only long-range interactions, and it was extended to account for Brownian motion by Lars Onsager. It assumes that the solvent is structure-less and that the solution is dilute, and the theory behind it implies that the electrostatic potential falls off exponentially when r is greater than the atomic radius due to screening by counter ions. For 10 points, identify this equation which is used to calculate the activity coefficients, and is named for a German and a Dutch scientist. 
[EX A]: Science

[EX Q]: This Vermont native's political positions included head of House and then Senate committees on territories, in which capacity he gave a speech telling opponents of expansion that "you cannot fetter the limbs of this young giant. " His support for expansion led him to favor repeal of the Missouri Compromise and he answered the Dred Scott decision by supporting popular sovereignty in what became known as the Freeport Doctrine. For 10 points, name this man who ran for president against John Bell, John C. Breckenridge and Abraham Lincoln, against the last of whom he had held a famous series of debates in Illinois.
[EX A]: History

[EX Q]: His time in office saw the promotion of a protectionist policy that was known as the "National Plan," it also saw corruption, as the Pacific Railroad scandal broke in 1873, forcing him to resign for five years. As a lawyer early in his career, he had earned the esteem of many for his defense of American raiders in the Rebellions of 1837. Elected alderman of the city of Kingston, the following year he and political allies like Etienne Cartier and George Brown accepted the Conservative party's nomination for a seat on the Legislative Assembly. Finally in 1857 he gained the highest office in the land. For ten points, name this politician who, following the Act of Dominion, became the first Prime Minister of Canada.
[EX A]:
History