Converting substance weight to molarity. Students with a background in chemistry are learning chemical calclations. We started with a definition of molarity. Now we are learning how to move between molarity and substance weight

 

Molarity is obtained by dividing the wt of substance by the substance's molecular weight. Molarity is measured in gram moles. We usually start knowing the weight of the substance. We obtain the substance's molecular weight from a table of atomic weights. If the substance is atomic then the weight from the table is the weight we use. If the substance is diatomic, such as hydrogen, we multiply the atomic weight by two because in chemical reactions hydrogen usually exists as H2. For more complicated compounds, we look up the weight of each multiplying the weight of each by the element's subscript because the subscript designates the number of atoms of that substance which appear in the compound. When all the elemental weights are obtained and multiplied by coefficients, the weights are totaled. That is the molecular weight of the substance.

 

Click to my lesson page lesson page lesson page on molarity

 

http://rpsec.usca.sc.edu//Classwork/731sp2004/Lesson/Selby/ (January, 2004)

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