Sample Problem 3.2
Calculating the Moles and Number of Formula Units in a Given Mass of a Compound
PROBLEM:
PLAN:
SOLUTION:
Ammonium carbonate is white solid that decomposes with warming. Among its many uses, it is a component of baking powder, fire extinguishers, and smelling salts. How many formula units are in 41.6 g of ammonium carbonate?
After writing the formula for the compound, we find M by adding the masses of the elements, convert the given mass (41.6 g) to moles using M, and then convert moles to formula units using Avogadro’s number.
The formula is (NH4)2CO3.
M = (2 x 14.01 g/mol N) + (8 x 1.008 g/mol H + (12.01 g/mol C) + (3 x 16.00 g/mol O)
= 96.09 g/mol
41.6 g (NH4)2CO3 x
2.61 x 1023 formula units (NH4)2CO3
x
=
| Previous slide | Next slide | Back to first slide | View graphic version |