Chemical Quantities Study Guide Pre-AP-Key
(Chapter 10 )
Name:______
1. Define the following vocabulary words:
Mole= unit of measurement for tiny particles (atoms, compounds)
Representative particles: substances that make-up matter (atoms, ionic compounds, molecules (covalent compounds).
Molar mass= atomic mass of one mole of a substance.
Percent composition of a compound= percent of mass an element contributes to a compound’s molar mass.
2. List the three common ways in which matter is measured and give an example of each.
Mass , quantity, and volume
3. Name the specific type of representative particle for each substance below.
a. Al(OH)3 (ionic compound) b. H2C2O4 (molecule/covalent) c. Na (atom)
d. Fe3P2 (ionic compound) e. H2O (molecule/covalent)
4. Identify the conversion needed to convert between these units of measurement.
a. moles and representative particles : 1 mole of a substance = 6.02x1023 particles of that substance
b. moles and mass of a substance: 1 mole of a substance = the molar mass of that substance
5. How many atoms of Sn are in 3.0 moles of Sn ? (mole-particles conversion)
=1.8x1024 atoms of Sn (2 significant figures)
6. How many moles of KCl are in 1.35x1021 compounds of KCl ?
= 0.00224 moles of KCl (3 significant figures)
7. How many compounds of SO2 are in 7.5 moles of SO2 ? 24 = 4.5x10 compounds of SO2 (2 significant figures)
8. How many moles of NaI are in 4.8x1024 compounds of NaI ?
= 8.0 compounds of NaI (2 significant figures)
9. Calculate the molar mass of each substance below. (Round to nearest tenth place)
a. Fe (molar mass of Fe= atomic mass of Fe) = 55.8 grams
b. O2 (molar mass of O2 = atomic mass of O2 = 16g x 2 = 32 grams
c. Ca3(PO4)2 Ca3: 40.1 x 3 = 120.3g
P2: 31.0 g x 2 = 62 g
+ O8: 16 x8 = 128 g
______
310.3 grams of Ca3(PO4)2
d.C4H9O2
C4: 12.0 x 4 = 48 g
H9: 1.0 x9 = 9.0 g
O2: 16.0x2 = +32.0 g
89.0 grams of C4H9O2
10. How many moles are in 15.5g of Al2O3?
Molar mass of Al2O3 = 102.0 g
= 0.152 moles of Al2O3
11. How many grams are in 2.5 moles of Mg3(PO4)2 ?
Molar mass of Mg3(PO4)2 = 264.4 g
= 660 grams of Mg3(PO4)2
12. How many grams are in 3.8 moles of Fe(OH)3? Molar mass of Fe(OH)3 = 106.8 g
= 410 grams of Fe(OH)3
13. How many moles are in 0.0688 g of AgCl?
Molar mass of AgCl = 143.4 g
= 4.80x10-4 grams of AgCl
14. Which substance below contains more particles? (show your work)
a. 1 mole of CO2 b. 1 mole of Ne c. 1 mole of Na2(CO3)
They all have the same number of particles: 6.02x1023 particles
15. Rank the following substances in decreasing order based on the number of moles present in each sample. (show work)
a.50 grams of C2H6 = 1.7 moles b. 50 grams of H2O2 = 1.5 moles c. 50 grams of CO= 1.8 moles
Ranking: CO > C2H6 > H2O2
16. What is the total mass of a mixture containing the following substances:
22 a. 3.5x10 ionic compounds of Na2SO4 = 8.3 g
b. 0.500 moles of H2O = 9.00 g
c. 7.23 grams of AgCl
Total mass = 24.5 grams of mixture
17. Two step conversion problems from practice sheet. (answers are on webpage)
18. Calculate the % composition of each compound below?
a. H2S H2: 2.0g
+ S : 32.1 g
= 34.1 g H2S
%H= 5.9 %
%S= 94.1 % b. (NH4)2C2O4 : N2: 28.0g
H8: 8.0 g
C2: 24.0 g
+ O4: 64.0 g
= 124 g of (NH4)2C2O4
%N= 22.6 %
%H=6.5
%C=19.4
%O=51.6
c.Mg(OH)2
Mg: 24.8 g
O2: 32.0 g
+ H2: 2.0 g
= 58.8 grams of Mg(OH)2
% Mg= 42.2
%O= 54.4
%H=3.4
d.Na3(PO4)
Na3: 69.0g
P: 31.0 g
+ O4: 64.0 g = 164 grams of Na3(PO4)
% Na= 42.1
%P= 18.9
% O= 39.0
19. Solve these problems using answers from question 18.
a. How many grams of sulfur is present in 3.54 g of H2S? = 3.54 x 0.941 = 3.33g of sulfur
b. How many grams of nitrogen is present in 25.0 g of (NH4)2C2O4 ?= 25.0 g x 0.226= 5.65 g of nitrogen
c. How many grams of magnesium is present in 97.4g of Mg(OH)2? = 97.4 g x 0.422 = 41.1 g of magnesium
d. How many grams of phosphorus is present in 804g of Na3(PO4)? = 804 g x 0.189 = 152 g of phosphorus