How many atoms are in a 2.5 mole sample of iron?
Start with the initial piece of information given in the problem. Multiply this term by a fraction that contains atoms of Fe in the numerator and moles of Fe in the denominator. Be sure that the numerical relationship between the numerator and denominator is valid. Notice that the units of moles Fe will cancel. The surviving units are atoms Fe, the desired units. In addition, the term (6×1023 atoms Fe) is equal to (1 mole Fe), so the fraction created with those two terms has a value that is equivalent to one. Many times it is possible to do more complex problems by using a single factor. While doing a problem with a single factor may sound easier, it can often become the source of errors. By doing a problem with several factors, each relationship that is needed to do the problem is more clearly defined, and the cancellation of units will indicate whether the problem is set up properly, or not. Question: How many atoms of Copper are present in a 1.2 kilogram sample? Answer: Again, start
