Chemistry 2

Grams-Grams

  1. Grams-Grams
    1. When we are working with substances in the lab we use balances to measure out how much substance to work with. So, we need to use the reading from the balance to make similar predictions about the mass of substances produced or needed to complete a chemical reaction.
    2. To do this, we need only do the appropriate conversions from grams to moles and back again to utilize the MOLE RATIO we can derive from the balanced chemical equation.
    3. Consider the following problem: Given the reaction between aluminum and oxygen to produce aluminum oxide, what mass of aluminum oxide would be produced if we started with 3.26g of aluminum?
    4. In order to solve this, we will need to use the chemical equation to tell us the relationship between the moles of Al and the moles of Al2O3. However, our Al quantity is in grams. First we must convert the grams to moles.
    5. Then, set up a mole ratio:
      0.121       x
      4 Al + 3 O2 ---> 2 Al2O3


    6. Then, convert the moles to grams.
    7. Now we have our answer: If we start with 3.26g of Al, we should expect to produce 6.16g of Al2O3.