Reactions and Reactivity: Chemical Calculations and Yields

A chemist measures out molecules or moles not by counting, but by weighing. The molar mass of a compound provides the connection between the mass of a sample of a substance and the number of moles of that substance in the sample. The molar mass can be used to set up more realistic calculations from equations.

For example, what if 46.0 g of sodium metal were put into a container of chlorine gas and allowed to completely react? How many grams of sodium chloride would be produced? Using a periodic table, the molar mass of sodium is found to be 23.0g/mol. The molar mass of sodium chloride is 58.5g/mol. This additional information is used to complete the calculation as before.

2Na(s) + Cl2 (g) → 2NaCl(s)

Furthermore, the amount of chlorine gas needed could be determined using a similar calculation. Calculation of volumes of gases will be addressed in the chapter on gases, but a similar calculation is used.


How many grams of chlorine gas are needed to completely react with 46.0 g Na?


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