Friday, July 24, 2015

How many moles are present in 550g of Zinc ?

In order to answer this question you need to know the molar mass of zinc, which is the mass of one mole of zinc atoms in grams. The periodic table that you included has only the symbols and atomic numbers for the elements and not the mass numbers.


The molar mass of zinc rounded to three significant digits is 65.4 grams per mole. Molar mass can be treated as a unit factor (conversion factor). Since we're starting out with grams and want to get the answer in moles, we will multiply the given quantity by 1 mole/65.4 grams. Grams cancels and we end up with moles:


550g x (1mole/65.4 g)=8.41 moles


When solving problems of this type it's a good idea to include the units then check to see that the final answer has the correct units. If you set the problem up incorrectly you'll know because the units will be incorrect.

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