Mole Review Worksheet---Key. This is extra credit for the test!
Name____Key___ Period_________________ Date___________________
**SHOW WORK!!**USE UNITS!!** SHOW WORK!!**USE UNITS!!** SHOW WORK!!**USE UNITS!!**
1. Calculate the molar mass of H3PO4.
98g
2. How many moles are in 25.2 g of Mg?
1.03 moles Mg
3. How many atoms are there in 56 moles of silver?
3.9 x 1025 atoms of Ag
4. How many atoms are in 17.1 grams of potassium?
2.63 x 1023 atoms of K
5. How many grams of calcium are there if you have 1.05 x 1022 atoms?
0.699 g of Ca
6. How many moles of SiO2 are in 15.5g?
0.258 moles SiO2
7. What is the mass of 0.780 mol Ca(CN)2
71.9 g Ca(CN)2
8. How many molecules are there in 25.0 g of C6H12O6 ?
8.36 x 10 22 molecules C6H12O6
9. If you have 9.13 x 1025 particles of NaCl, how many grams would you have?
8,860 g NaCl
10. How many H atoms are in 17.5 g (NH4)2C2O4?
6.80 x 1023 H atoms
11. How many oxygen molecules are in 3.36 L of oxygen gas at STP?
9.02 x 1022 molecules of O2
12. Determine the volume in liters occupied by 14 g of nitrogen gas at STP.
11.2 L of N2
13. Aspartame is an artificial sweetener that is 160 times sweeter than sucrose (table sugar) when dissolved
in water. It is marketed by G.D. Searle as Nutra Sweet. The molecular formula of aspartame is C14H18N2O5 .
a) Calculate the molar-mass of aspartame.
294.02 g/mole
b) How many moles of molecules are in 10 g of aspartame?
0.034 moles
c) What is the mass in grams of 1.56 moles of aspartame?
459 g of aspartame
d) How many molecules are in 5 mg of aspartame?
1 x 1019 molecules of aspartame
e) How many atoms of nitrogen are in 1.2 grams of aspartame?
4.9 x 1021 atoms of N
14. Calculate the percent composition of H2S.
5.87 % H & 94.13 % S
15. Calculate the percent composition of ethane C2H6.
20 % H & 80 % C (notice that even though there are more atoms of H, the percent mass is lower because
the molar mass is so small)
16. What is the empirical formula of a compound containing 79.8% C and 20.2% H?
6.64 mol C & 20.2 mole H
Empirical formula is
CH3
17. Calculate the empirical formula for a compound containing 67.6% Hg, 10.8% S, and 21.6% O.
0.337 mole Hg
0.337 mole S
1.35 mole O
1 Hg : 1 S : 4 O
Empirical formula is H2SO4
18. Calculate the empirical and molecular formulas for a compound containing 94.1% O and 5.9%H that has a
molar mass of 34 g.
5.88 moles of O
5.90 moles of H
1O:1H
HO has a mass of 17, 34/17=2 so the
Empirical Formula is HO
Molecular Formula is H2O2
19. Calculate the molecular formula for a compound containing 40.0% C, 6.6% H, and 53.4% O with a molar
mass of 120 g.
3.33 moles C
6.67 moles H
3.33 moles O
1C:1H:1O
Empirical Formula is CH2O
Mass of CH2O is 30 g. 120/30=4 so the
Molecular Formula is C4H8O4