The MOLE课件.ppt

The MOLE;AVOGADRO’S NUMBER;AVOGADROS Number;That once one “combining mass” of an element was known, it must have the Same number of atoms as one combining mass of a different element. By the end of the nineteenth century, the SIZE of that number had been determined And a word, meaning “a heap” had been invented as the unit for that number. AVOGADRO’S NUMBER: 6.02 x 1023 = 1 mole;The natural substance with the LEAST MASS is;Finding the Mass in grams of one molecule of H2 and 1 atom of H:;Review;REVIEW;Problem solving in quantitative chemical problems.;For example in practice prob. 1;Sample prob 7.2;2.12 moles of C3H8 contains;2.12 moles of C3H8 contains;Gather all given known information:;Frequently, lab measurable quantities are given or wanted.;Solving a gram to mole problem:;For example, C5H10;How many moles is 65.0 g of (NH4)3(PO4)?;The gram formula mass of ammonium phosphate is;Fill in the blanks:;Answer: ;And the answer is;The reverse procedure gives grams when moles are given.;To set up the problem, ;For gases at standard temperature of 0oC and 1 atm.;Here are some molar volume questions:;More molar volume questions;Did you notice the “trick” question?;and;% composition and moles;Using percent composition.;Finding empirical formulas;What is the formula for this compound?;Fill in the blanks in each step for finding the formula. The first element in the formula is C.;Insert the number of moles you have found in the subscript variables. CH Divide the smaller subscript into the larger subscript. In this case, the rounded integers will be even. C6.25H24.75 24.75/6.25 ~ 4 C1H4 or CH4 The substance is methane.;A more interesting compound is composed of ;1.25 moles of Fe are present for every 1.88 moles of O. Dividing 1.88/1.25 yields a ratio of 1.5/1 of O. Fe1O1.5 is the result. But subscripts must be integers. Multiplying each subscript by 2 yields the correct empirical formula, Fe2O3. 3:4 or 4:3 ratios are also possible. ; If there are 3 or more elements,