Study Sheet of Molarity and Stoichiometry
Posted by Professor Cram in Molarity and Stoichiometry
Molarity and Stoichiometry (Smartacus Study Sheet)
Definitions
- Avogadro's Number is number of molecules in a mole of a single element .
- Molarity is the concentration of a compound, or "solute", in a solution. It is typically expressed in moles/liter.
- Molar Mass is a measure of the mass of one mole of a molecule or element. It is usually expressed in grams/mole.
- Mole Abbreviated mol, a mole is the quantity of a single element such that its mass in grams is equal to its atomic mass. For example, Oxygen has an atomic mass of 15.9994, so a mole of Oxygen has a mass of 15.9994 grams.
Calculating Molar Mass:
- Calculating a molecule's molar mass requires multiplying the number of each element by its atomic mass.
- Example: Given a water molecule (H20), where the atomic mass of oxygen is 15.9994 and the atomic mass of hydrogen is 1.0079:
Molar Mass = (1.0079)2 + (15.9994) or 18.0152 grams/mole
Mole Conversions:
- Converting between the number of moles or mass in grams of a molecule-sample requires first finding molar mass of a single molecule.
- Example: Given a water molecule (H20), where the atomic mass of oxygen is 15.9994 and the atomic mass of hydrogen is 1.0079:
Molar Mass = (1.0079)2 + (15.9994) or 18.0152 grams/mole
- Once a single molecule's molar mass is found, you can convert between the mass (in grams) and the number of moles.
Mass of the sample = (molar mass) x (number of moles in the sample)
Moles in the sample = (Mass of the sample)/(molar mass)
Molarity:
- Molarity is typically expressed as moles/liter.
- Given any two of the molarity, moles of solute, or liters of solution:
Molarity = (Moles of Solute)/(Liters of Solution)
Moles of Solute = (Molarity) x (Liters of Solution)
Liters of Solution = (Moles of Solute)/(Molarity)
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