7.1: “Avogadro’s Number and Molar Conversions” Day 3
1. Changing Particles
a.
Mass
You need ______ steps to change number of particles to mass, in grams:
1.
Change particles to _____________ using ____________________ number.
2. Change moles to ____________ using the ___________
_____________.
b. ________ different conversion factors must be used!
2. Changing Particles
Mass; Sample Problem C, pg. 231
Find the mass in grams of 2.44 X 1024 atoms of carbon, whose molar mass is 12.01 g/mol.
1.
Start with what you know: 2.44 X 1024 atoms C
2. Use Avogadro’s number as a conversion factor to change atoms C
2.44 X 1024 atoms C X
1 mol C
=
moles C:
4.05 mol C
6.022 X 1023 atoms C
3. Now, use molar mass of carbon to change moles C
4.05 mol C X
12.01 g C
=
mass (in grams) of C:
48.6 g C (3 sig figs)
1 mol C
3. Changing Particles
Mass; Practice #1
Find the mass in grams of 6.12 X 1014 formula units of rhenium dioxide, ReO2,
218.21 g/mol.
1.
Start with what you know:
2. Use Avogadro’s number as a conversion factor to change
form. units ReO2
moles ReO2:
3. Now, use molar mass of ReO2 to change moles ReO2
mass (in grams) of ReO2:
4. Changing Mass
Particles
a. Converting from __________ to number of particles is simply the
________________ of what you’ve just done.
b. You need _______ steps to change number of particles to mass:
1.
Change ________ to moles using _____________ _____________
2. Change moles to particles using ____________________ number.
3. Two different _______________ _____________ must be used!
4. Changing Mass
Particles; Sample Problem D, pg. 232
Find the number of molecules present in 47.5 g of glycerol, C3H8O3. The molar mass of
glycerol is 92.11 g/mol.
1.
Start with what you know: 47.5 g C3H8O3
2. Use molar mass of C3H8O3 to change mass C3H8O3 to moles C3H8O3:
47.5 g C3H8O3 X 1 mol C3H8O3
=
.516 mol C3H8O3
92.11 g C3H8O3
3. Now, use Avogadro’s number to change moles
.516 mol C3H8O3 X
molecules:
6.022 X 1023 molecules C3H8O3 = 3.11 X 1023 molecules C3H8O3
1 mol C3H8O3
5. Changing Mass
(3 sig figs)
Particles; Additional Practice
Determine the number of atoms present in 54.3 g of cobalt, Co.
1.
Start with what you know:
2. Use molar mass of Co to change mass Co
moles Co:
3. Now, use Avogadro’s number to change moles Co
atoms Co: