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