Chemistry
Minniear
Mole – Mass calculations EXTRA plus KEY
You cannot go directly from mass to # atoms/molecules/formula units or back – you must go
through moles first.
mass ↔ mole ↔ # atoms/molecules/formula units
Mass to moles
or
moles to mass
6.02 x 1023/ 1 mole
or
1 mole/6.02 x 1023
From the periodic table
1. What is the mass of 2.54 mol of Al.
2. How many grams is 5.26 x 1015 molecules of O2?
3. How many moles are in 200.0 g of Au?
4. Find the mass of 3.50 mol of C.
5. Find the number of molecules of CO2 in 25.0 g of CO2.
6. 10.0 g of Na = _______ mol Na.
7.How many formula units in 6.75 mol NaCl?
8. Find the gram-molecular mass of H2O.
Chemistry
9. Find the mass of 1 mole of (NH4)2CO3.
10. What is the mass of 8.25 x 1028 formula units of H2CO3?
11. Find the gram-atomic mass of Zinc.
12. 2.25 x 1016 atoms of As has a mass of ____________ g.
13.What is the mass of 2 moles of NaCl?
14. 2.00 g of NaCl contains ________ formula units?
15. 3.75 mol of ZnSO4• 5H2O = __________ formula units?
Minniear
Chemistry
Minniear
Mole – Mass calculations EXTRA plus KEY
1. What is the mass of 2.54 mol of Al.
(
2.54mol 26.98g
)(
)  68.5g
1
1mol
From the periodic table
2. How many grams is 5.26 x 1015 molecules of O2?
(
5.26x1015 molecules O2
1mol O2
32.00g O2
)(
)(
)  2.80x10 7 g
23
1
1mol O2
6.022x10 molecules O2
# of whatevers in a mole of whatever.
From the periodic table.
3. How many moles are in 200.0 g of Au?
(
200 .0g Au 1mole Au
)(
)  1.015 mol
1
197 g Au
From the periodic table
4. Find the mass of 3.50 mol of C.
(
3.50 mol C 12.01 g C
)(
)  42.0 g
1
1 mol
5. Find the number of molecules of CO2 in 25.0 g of CO2.
(
25.0g CO2 1 mol CO2 6.022x1023
)(
)(
)  3.42x1023 molecules
1
44.01g
1mol
Molar mass CO2
O:(2)(16.00) = 32.00 g
C:(1)(12.01) = 12.01 g
44.01 g
Chemistry
Minniear
6. 10.0 g of Na = _______ mol Na.
(
10.0g Na 1 mol Na
)(
)  0.435 mol
1
22.99g Na
7. How many formula units in 6.75 mol NaCl?
6.75 mol NaCl 6.022x1023 formula units
(
)(
)  4.06x1024 formula units
1
1 mole
The number of whatevers in a mole of whatever does not depend on mass.
8. Find the molar mass of H2O.
H: (2)(1.01 g) = 2.02 g/mol
O: (1)(16.00g)= 16.00 g/mol
18.02 g/mol
9. Find the mass of 1 mole of (NH4)2CO3.
N:(2)(14.01) = 28.02 g/mol
H:(8)(1.01) = 8.08 g/mol
C:(1)(12.01) = 12.01 g/mol
O:(3)(16.00) = 48.00 g/mol
96.11 g/mol
10. What is the mass of 8.25 x 1028 formula units of H2CO3?
62.03 g H2CO3
8.25x1028 formula units
1 mol
(
)(
)(
)  8.50x10 6 g
23
1
1 mol
6.022x10 formula units
Your calculator gave something like 8,497,965.8 grams as an answer. Sig figs.
11. Find the molar mass of Zinc.
Straight from the periodic table : 65.38 g/mol
Chemistry
Minniear
12. 2.25 x 1016 atoms of As has a mass of ____________ g.
(
2.25x1016 atoms
1 mol
74.92 g As
)(
)(
)  2.80x10 6 g
23
1
1
mol
6.022x10 atoms
13. What is the mass of 2 moles of NaCl?
2 mol NaCl 58.44 g NaCl
(
)(
)  116 .88 g
1
1 mol
Molar mass of NaCl:
Add the mass of 1 mole of Na and
1 mole of Cl from the periodic
table
14. 2.00 g of NaCl contains ________ formula units?
2.00g NaCl 1 mol NaCl 6.022x1023 formula units
(
)(
)(
)  2.06x1022
1
58.44 g NaCl
1 mol
15. 3.75 mol of ZnSO4• 5H2O = _________ formula units?
(
3.75 mol 6.022x1023 formula units
)(
)  2.26x1024
1
1 mol
The number of whatevers in a mole of whatever does not depend on mass.