Question #7908b

1 Answer
Jun 12, 2017

Answer:

#65.0# #"g N"_2#

Explanation:

Any time you want to convert between moles and grams of a substance, you must know that substance's molar mass, which is the mass of one mole of that substance. (One mole is equal to Avogadro's number (#6.022xx10^23#) of individual particles/molecules of that substance.)

To find the molar mass of a nitrogen molecule, we'll first realize its chemical formula, which is #"N"_2#.

Most periodic tables list the molar masses (same number as atomic mass) of all the elements under their chemical symbol. For nitrogen, the molar mass is #14.01"g"/"mol"#, that is, one mole of pure nitrogen atoms has a mass of #14.01# grams.

Since there are two nitrogen atoms per nitrogen molecule, the molar mass of #"N"_2# is double that of elemental nitrogen:

#2 xx 14.01"g"/"mol" = color(red)(28.02"g"/"mol"#

Now, we can use dimensional analysis to convert between moles and grams of #"N"_2#:

#2.32# #cancel("mol N"_2)((color(red)(28.02"g N"_2))/(1cancel("mol N"_2))) = color(blue)(65.0# #color(blue)("g N"_2#

rounded to #color(purple)(3# significant figures, the amount given in the problem.

Thus, #2.32# moles of pure nitrogen gas has a mass of #color(blue)(65.0# grams.