Chapter-10: Chemical Quantities Practice Calculations
Mole-Mass-Volume and % Composition Problems:
1.
What is the mass of 7.50 moles of sulfur dioxide (SO2)?
Ans: 481 g
2.
What is the mass of 0.438 mole of ammonium chloride (NH4Cl)?
Ans: 23.4 g
3.
How many moles are there in 250.0 g of sodium phosphate (Na3PO4)?
Ans: 1.524 mol
4.
How many moles are there in 993.6 g of potassium sulfate (K2SO4)?
Ans: 5.70 mol
5.
How many atoms are there in 3.00 moles of sodium (Na)?
Ans: 1.81 x 1024 atoms
6.
How many atoms are there in 1.638 x 10-9 mole of lithium (Li)?
Ans: 9.86 x 1014 atoms
7.
How many molecules are there in 4.55 moles of nitrogen (N2)?
8.
How many atoms of nitrogen (N) are there in 2.18 moles of nitrogen (N2)?
Ans: 2.62 x 1024 atoms
9.
How many atoms are there in 0.663 mole of water (H2O)?
Ans: 1.2 x 1024 atoms
Ans: 2.74 x 1024 molecules
10. How many moles are there in 15.5 x 1023 molecules of carbon dioxide (CO2)? Ans: 2.57 mol
11. How many moles are there in 1.326 x 1012 molecules of carbon tetrachloride (CCl4)?
Ans: 2.2 x 10-12 mol
12. What is the volume occupied by 4.20 moles of oxygen gas (O2) at STP?
Ans: 94.1 dm3
13. What volume does 0.0147 mole of nitrogen dioxide gas (NO2) occupy at STP?
Ans: 0.329 L
14. How many moles are there in 45.0 dm3 of methane gas (CH4) measured at STP?
Ans: 2.01 mol
15. How many moles are there in 0.335 dm3 of argon gas (Ar) at STP?
16. Calculate the percentage composition of lithium oxide (Li2O).
Ans: 1.5 x 10-2 mol
Ans: Li = 46.5% O = 53.5%
17. What is the percentage composition of dinitrogen tetroxide (N2O4)? Ans: N = 30.4% O = 69.6%
18. What is the percentage composition of a carbon-oxygen compound, given
that a 95.2 g sample of the compound contains 40.8 g of carbon and 54.4 g of oxygen?
Ans: C = 42.9%
O = 57.1 %
19. What is the percentage composition of a sulfur-chlorine compound, given that a 30.9-g sample of
the compound is found to contain 9.63 g of sulfur and 21.3 g of chlorine? Ans: S = 31.1%
Cl = 68.9%
20. A sample of a compound that has a mass of 0.432 g is analyzed. The sample is found to be made up
of oxygen and fluorine only. Given that the sample contains 0.128 g of oxygen, calculate the
percentage composition of the compound.
Ans: O = 29.6%
F = 70.4%
21. Find the empirical formula of a compound, given that the compound is found to be 47.9% zinc (Zn)
and 52.1% chlorine (Cl) by mass. (Zn = 65.4 g/mol; Cl = 35.5 g/mol) Ans: ZnCl2
22. Find the empirical formula of a compound, given that a 48.5-g sample of the compound is found to
contain 1.75 g of carbon (C) and 46.75 g of bromine (Br).
Ans: CBr4
23. What is the empirical formula of a compound, given that a 212.1-g sample of the compound contains
42.4 g of hydrogen (H) and 169.7 g of carbon (C)? What is the molecular formula of the compound,
given that it has a gram molecular mass of 30.0 g/mol?
Ans: C2H6
24. A compound is known to have a gram molecular mass of 391.5 g/mol. Find the empirical and the
molecular formulas of the compound, given the results of an analysis of a 310.8-g sample that reveals
that the sample contains only boron (B) and iodine (I). The mass of the iodine in the sample is found
to be 302.2 g.
Ans: BI3
25. Calculate each of the following for the compound: ammonium sulfate, (NH4)3PO4
a) the molar mass of the compound
150 g
b) the mass of cation in 2.179 x 1023 molecules of compound
19.5 g
c) the percent composition of cation
36.2%
d) the number of anions represented by the formula
1
e) the number of hydrogen atoms represented by the formula
12
f) the total number of atoms represented by the formula
20
26. Calculate each of the following for the compound: sodium carbonate, K2CO3
a) the molar mass of the compound
b) the mass of carbon in 3.734 L of gaseous compound
c) the mass of potassium represented by the formula
d) percent by mass of oxygen in K2CO3
e) total number of ions represented by the formula
f) the total number of atoms represented by the formula
138.2 g
2.0 g
78.2 g
34.7%
3
6