CHM 2045 Lecture Notes - Lecture 5: Limiting Reagent, Reagent, Magic 2Ch
18 Feb 2016
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Law of conservation of mass: the mass and/or moles of the reactants is equivalent to that of the products. The number of moles on one side of the reaction should be equal to that of the other side. Never change the subscripts of an element, only change the coefficients. First balance the element that only appears in one product or reactant. Balance the elements that appear in two or more reactants or products last. Ex) methanol burns in air according to the equation 2ch3oh + 3o2 . If 209 g of methanol are used up in the combustion reaction, what mass of water is produced: grams ch3oh moles ch3oh moles h2o grams h2o, (209 g ch3oh)*(1 mol ch3oh/32. 00 g)*(4 mol h2o/2 mol. Ch3oh)*(18. 02 g /1 mol h2o) = 235 g h2o. Ex) in one process, 124 g of al is reacted with 601 g of fe2o3, given that 2al + fe2o3 al2o3 + 2fe.
