Chemical Quantities slideshow

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Chemical Quantities
The Mole

2. What is a Mole?

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Counting with Moles
Chemists use mole as a specified number of particles
• A mole (mol) of a substance is 6.022 × 1023
particles (atoms, molecules, or formula units)
• 6.022 × 1023
is called Avogadro’s number

4. The table below summarizes the relationship
between representative particles and moles of
substances.
Representative Particles and Moles
Substance Representative
particle
Chemical
formula
Representative
particles in 1.00
mol
Copper Atom Cu 6.022 × 1023
Atomic nitrogen Atom N 6.022 × 1023
Nitrogen gas Molecule N2 6.022 × 1023
Water Molecule H2O 6.022 × 1023
Calcium ion Ion Ca2+
6.022 × 1023
Calcium fluoride Formula unit CaF2 6.022 × 1023
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Counting with Moles

5. 1 mol = 6.02 × 1023
representative particles
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Converting Number of Particles - Moles
1 mol
6.02 × 1023
particles
6.02 × 1023
particles
1 mol
or

6. https://www.jokejive.com/topic/chemistry+mole

7. How many moles of Mg is 1.25 × 1023
atoms of Mg?
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Converting Number of Particles - Moles
1 mol
6.022 × 1023
atoms
6.022 × 1023
atoms
1 mol
or
1.25×1023
atoms Mg ×
= 0.208 mol Mg
The desired conversion is atoms → moles

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How many atoms are in 2.12 mol of propane (C3H8)?
The desired conversion is: moles → atoms
Converting Number of Moles - Particles
1 mol
6.022 × 1023
atoms
6.022 × 1023
atoms
1 mol
or
2.12 moles C3H8 ×
= 1.28×1024
molecules

9. The Mass of a Mole of an Element
The mass of a mole of an element is the
atomic mass in grams
• For carbon, the molar mass is 12.0 g
• For atomic hydrogen, the molar mass is 1.0 g

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1 mol of carbon atoms = 12.0 g
1 mol of sulfur atoms = 32.1 g
1 mol of iron atoms = ? g

11. SO2
1S 32.06 amu
2O + 2 x 16.00 amu
SO2 64.07 amu
1 molecule of SO2 weighs 64.07 amu
1 mole of SO2 weighs 64.07 g
For any molecule
molecular mass in amu = molar mass in grams
SO2

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The Mass of a Mole of a Compound
1 mol of para-dichlorobenzene (C6H4Cl2)
molecules (moth crystals) = 147.0 g
1 mol of water (H2O) molecules = 18.0 g
1 mol of glucose
(C6H12O6) molecules
(blood sugar) = ?

13. What is the molar mass of hydrogen peroxide
(H2O2)?
molecular formula = H2O2
mass of 1 mol H = 1.0 g H
mass of 1 mol O = 16.0 g O
mass 1 mol H2O2 = 2x1.0g H + 2x16.0g O = 34.0 g
molar mass of H2O2 = 34.0 g/mol
https://www.youtube.com/watch?v=ca6aKZPBonI&feature=share
https://www.toppr.com/ask/question/compare-the-structure-of-h2o-and-

14. https://www.pinterest.com/pin/chemistry-mole-problems-square-sticker--669488300872526383/

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Chemical Quantities
Mole-Mass and Mole-Volume
Relationships

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molar mass (g)
1 mol
1 mol
molar mass (g)
and
The conversion factors are based on the
relationship molar mass = 1 mol
Mole-Mass and Mole-Volume Relationships

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What is the mass, in grams, of 9.45 mol Al2O3?
The desired conversion is: moles → grams
Converting Number of Moles - Grams
102.0 g
1 mol
9.45 mol Al2O3 × = 964 g Al2O3

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How many moles of iron(III) oxide (Fe2O3) are
contained in 92.2 g?
The desired conversion is: grams → moles
Converting Number of Moles - Grams
1 mol Fe2O3 = 111.6 g Fe + 48.0 g O = 159.6 g
2 mol Fe × = 111.6 g Fe
55.8 g Fe
1 mol Fe
3 mol O × = 48.0 g O
16.0 g O
1 mol O

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How many moles of iron(III) oxide (Fe2O3) are
contained in 92.2 g?
The desired conversion is: grams → moles
Converting Number of Moles - Grams
92.2 g Fe2O3 ×
1 mol Fe2O3
159.6 g Fe2O3
= 0.578 mol Fe2O3

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Converting Number of Moles - Volume
Avogadro’s hypothesis states that equal volumes of
gases at the same temperature and pressure contain
equal numbers of particles
Standard temperature and pressure (STP) means
temperature of 0°C and
pressure of 101.3 kPa, or 1 atmosphere (atm)

21. Avogadro’s hypothesis
https://chem.libretexts.org/
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•At STP, 1 mol, or 6.02 × 1023
representative
particles, of any gas occupies a volume of 22.4 L
•22.4 L is the molar volume of a gas
Converting Number of Moles - Volume

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22.4 L
1 mol
1 mol
22.4 L
and
The conversion factors for these calculations are
based on the relationship 22.4 L = 1 mol at STP
Converting Number of Moles – Volume

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Determine the volume (L) of 0.60 mol SO2 gas at STP
The desired conversion is: moles → volume (L)
Converting Number of Moles - Volume
22.4 L SO2
1 mol
0.6 mol SO2 × = 13 L SO2

24. The density of a gaseous compound containing carbon and
oxygen is found to be 1.964 g/L at STP. What is the molar mass
of the compound?
The desired conversion is: density → molar mass
Converting Number of Moles - Volume
density = 1.964 g/L
1 mol of gas at STP = 22.4 L
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= 44.0 g/mol
1.964 g
1 L
22.4 L
1 mol
×

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26. N2(g) + 3H2(g)  2NH3(g)
The Haber Process for the manufacture of
ammonia NH3 produced industrially by the
reaction of nitrogen with hydrogen

27. Number of Molecules
Nitrogen and hydrogen will always react to form
ammonia in a 1:3:2 ratio of molecules.
1  ( )+ 3  ( )  2  ( )
6.02  1023
molecules N2
6.02  1023
molecules H2
6.02  1023
molecules NH3
N2(g) + 3H2(g)  2NH3(g)

28. A balanced chemical equation tells you the
number of representative particles, it also tells
you the number of moles
1 mol N2 + 3 mol H2  2 mol NH3
Moles
N2(g) + 3H2(g)  2NH3(g)

29. Mass
28g N2 + (32g H2)  (217g NH3)
28g N2 + 6g H2  34g NH3
N2(g) + 3H2(g)  2NH3(g)

30. 1 mol of a gas at STP has a volume of 22.4 L
22.4 L N2 + 67.2 L H2  44.8 L NH3
22.4 L N2 + (322.4 L H2)  (222.4 L NH3)
Volume
N2(g) + 3H2(g)  2NH3(g)

31. N2(g) + 3H2(g) 2NH3(g)
+
2 atoms N + 6 atoms H 2 atoms N and 6 atoms H
1 molecule N2 + 3 molecules H2 2 molecules NH3
1  + 3  2 
1 mol N2 + 3 mol H2 2 mol NH3
28 g N2 + 3  2 g H2 2  17 g NH3
34 g reactants 34 g products
Assume
STP
22.4 L N2
+
67.2 L H2 44.8 L NH3
6.02  1023
molecules N2
( ) 6.02  1023
molecules H2
( ) 6.02  1023
molecules NH2
( )
22.4
L
22.4
L
22.4
L
22.4
L
22.4
L
22.4
L

32. 22.4 L
1 mol
1 mol
22.4 L
and
molar mass (g)
1 mol
1 mol
molar mass (g)
and
1 mol
6.02 × 1023
particles
6.02 × 1023
particles
1 mol
and
Converting Number of Moles – Grams – Volume - Particles

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34. https://slideplayer.com/slide/724492/

35. https://www.slideserve.com/melosa/chemical-change-17-3
2 mol NaHCO3 decompose into 1 mol Na2CO3
1 mol NaHCO3 decomposes into 0.5 mol Na2CO3
0.5 mol NaHCO3 decomposes into 0.25 mol Na2CO3

36. https://www.slideserve.com/melosa/chemical-change-17-3
84 g NaHCO3 decompose into 53 g Na2CO3
2 mol NaHCO3 decomposes into 1 mol Na2CO3
8.4 g NaHCO3 decompose into ? Na2CO3

37. https://www.slideserve.com/melosa/chemical-change-17-3
X g NaHCO3 decompose into Y g Na2CO3

38. Percent Composition?
The percent composition by mass of a compound represents
the percent that each element in a compound contributes to
the total mass of the compound

39. https://www.youtube.com/watch?v=Snnt0CpkWSM

40. What is the percent composition of H and O in water (H2O)?
Step 1: n x molar mass from the formula H2O
2 mol Hydrogen x 1.01g = 2.02g
1mol Oxygen x 16.00g = 16.00g
molar mass of water = 18.02g
Percent Composition?
Step 2:
(2.02 g H / 18.02 g H2O) x 100 % = 11.21% H
(16.00 g O / 18.02 g H2O) x 100 % = 88.79% O
Your percentages should add up to 100%
n x molar mass of element
molar mass of compound
x 100%

41. n molar mass of element
molar mass of compound
x 100%
C2H6O
%C =
2 x (12.01 g)
46.07 g
x 100% = 52.14%
%H =
6 x (1.008 g)
46.07 g
x 100% = 13.13%
%O =
1 x (16.00 g)
46.07 g
x 100% = 34.73%
52.14% + 13.13% + 34.73% = 100.0%

42. An 8.20g piece of magnesium combines completely with 5.40g of
oxygen to form magnesium oxide.
What is the percent composition of the magnesium oxide?
Step 1: Find the mass of the compound
8.20g Mg + 5.40g O = 13.60 g
Step 2: Find the percent by mass of each element
%Mg = 8.20g x 100% = 60.29% of Mg
%O = 5.40g x 100% = 39.71 % of O
13.60g
13.60g

43. Your Turn:
What is the percent composition of glucose (C6H12O6)
Step 1: figure out the molar mass:
Step 2:
Molar mass of C6H12O6 = 180.2 g/mol
n x molar mass of element
molar mass of compound
x 100%
Hydrogen H 7%
Carbon C 40%
Oxygen O 53%

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A hydrate is a crystalline compound in which ions are
attached to one or more water molecules.
Na2CO3 10H2O, CuSO4 5H2O
Substances without water built into the formula are
called anhydrates
What is a hydrate?

46. https://www.youtube.com/watch?v=zRjS6f6I9aQ

47. Step 1: Calculate the formula mass for the hydrate
• Na = 2 x 23.0 g/mol = 46.0 g/mol
• C = 1 x 12.0 g/mol = 12.0 g/mol
• O = 3 x 16. 0 g/mol = 48.0 g/mol
• H2O = 10 x 18.0 g/mol = 180 g/mol
Formula mass of hydrate = 286 g/mol
How to Calculate % Composition
Problem: What is the percentage by mass of water in sodium carbonate
crystals (Na2CO3 10H2O)?

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% by mass = x 100
% H2O by mass = x 100
% H2O by mass = 62.9 %
Problem: What is the percentage by mass of water in sodium carbonate
crystals (Na2CO3 10H2O)?

49. https://depts.washington.edu/chem/courses/labs/142labs/CompDemo.html
Practice problem:
A sample of hydrate sodium carbonate Na2CO3xH2O has a mass of
71.5 g. After heating in a crucible, the anhydrous sodium
carbonate Na2CO3 has a mass of 26.5 grams. Calculate the % water
Mass Na CO .xH O: 71.5 g
₂ ₃ ₂
Mass Na CO : 26.5 g
₂ ₃
Mass lost H O = 71.5 g - 26.5 g =
₂ 45.0 g
%H O = 45.0 g / 71.5 g × 100% =
₂ 62.9%

50. Calculate the percentage composition by mass of the following compounds
1) HgO
2) Na2S
3) (NH4)2S
4) Sr(NO3)2