Download Chapter 2 Overview

Chapter 2 Overview
! all matter, whether liquid, solid, or gas,consists of atoms,
which form molecules
! the identity of an atom and its chemical behavior is
strictly defined by the number of electrons in the outer
electronic sphere, which equals to the number of protons in
the nucleus
! the atomic weight is the combined mass of protons and
neutrons in the nucleus. Each contributes one unit of mass.
The mass of the electrons is negligible
Chapter 2 Overview
6 electrons
6 electrons
6 no+
6p
12
7 no+
6p
13
C
C
ISOTOPES OF CARBON
number of
neutrons
N = Mass - Z
atomic number
number of protons
Periodic Table
Main Group Elements:Group Number corresponds to ionic charge
Chapter 2 Overview
Ionic compounds: Simple salts. Charges Balanced
NaCl
Na+
Cl–
LiI
Li+
I–
Cs2SO4
Cs+
SO42–
Fe2(CO3)3
Fe3+
CO32–
(NH4)3PO4
NH4+
PO43–
Chapter 2 Overview
Molecular Weight = Sum of Atomic Weights
MW(NaCl) = Atomic Mass of Na + At. Mass of Cl
Chapter 2 Sample Problem
2.132. Succinic acid is an important metabolite in biological
energy production. Give the molecular formula, empirical
formula, and molecular mass of succinic acid.
O H H
O
C C C C
H O H H O H
succinic acid
Chapter 2 Sample Problem
2.132. Succinic acid is an important metabolite in biological
energy production. Give the molecular formula, empirical
formula, and molecular mass of succinic acid.
O H H
• mol. formula:count all atoms: C4H6O4
O
C C C C
H O H H O H
succinic acid
Chapter 2 Sample Problem
2.132. Succinic acid is an important metabolite in biological
energy production. Give the molecular formula, empirical
formula, and molecular mass of succinic acid.
O H H
• mol. formula:count all atoms: C4H6O4
O
C C C C
H O H H O H
succinic acid
• empirical formula: C2H3O2 (whole numbers!)
Chapter 2 Sample Problem
2.132. Succinic acid is an important metabolite in biological
energy production. Give the molecular formula, empirical
formula, and molecular mass of succinic acid.
O H H
• mol. formula:count all atoms: C4H6O4
O
C C C C
H O H H O H
succinic acid
• empirical formula: C2H3O2 (whole numbers!)
• MW = 4!12.01 + 6!1.008 + 4!16.00 = 118.09
Chapter 2 Sample Problem
2.128. How can iodine (Z = 53) have a higher atomic number yet
lower atomic weight than tellurium (Z = 52)?
Stoichiometry: The Mole
describes quantitative aspects of chemical reactions
One mole (1 mol) is 6.022!1023 molecules (ions, atoms, etc.)
Avogadro’s number
M = MW
molar
weight (g/mol)
molecular
weight
Stoichiometry
MW(H2) = 2.02
M = 2.02 g/mol
MW(NaCl) = 58.44
M = 58.44 g/mol
MW(AgNO3) = 169.91
M = 169.91 g/mol
1 : 1 ratio of NaCl and AgNO3:
58.44 g of NaCl and 169.91 g of AgNO3
or
etc
0.584 g of NaCl and 0.169 g of AgNO3
Stoichiometry
mass in grams
m (g)
M (g/mol) =
n (mol)
molar
weight (g/mol)
number of mols
Stoichiometry
mass in grams
m (g)
M (g/mol) =
n (mol)
molar
weight (g/mol)
number of mols
m (g)
n (mol) =
M (g/mol)
Stoichiometry
mass in grams
m (g) = n (mol) ! M (g/mol)
number of moles (mol)
molar
weight (g/mol)
Sample Problem 3.2
Ammonium carbonate, is a white solid that decomposes with
warming. Among its many uses, it is a component of baking powder,
fire extinguishers, and smelling salts. How many moles are in 41.6 g
of ammonium carbonate?
Sample Problem 3.2
Ammonium carbonate, is a white solid that decomposes with
warming. Among its many uses, it is a component of baking powder,
fire extinguishers, and smelling salts. How many moles are in 41.6 g
of ammonium carbonate?
• divide given mass by mol weight
Sample Problem 3.2
Ammonium carbonate, is a white solid that decomposes with
warming. Among its many uses, it is a component of baking powder,
fire extinguishers, and smelling salts. How many moles are in 41.6 g
of ammonium carbonate?
• divide given mass by mol weight
• what is ammonium carbonate?
n (mol) =
m (g)
M (g/mol)
Sample Problem 3.2
Ammonium carbonate, is a white solid that decomposes with
warming. Among its many uses, it is a component of baking powder,
fire extinguishers, and smelling salts. How many moles are in 41.6 g
of ammonium carbonate?
n (mol) =
m (g)
M (g/mol)
• divide given mass by mol weight
• what is ammonium carbonate? NH4+ ,CO32– " (NH4)2CO3
• what is its mol. weight?
Sample Problem 3.2
Ammonium carbonate, is a white solid that decomposes with
warming. Among its many uses, it is a component of baking powder,
fire extinguishers, and smelling salts. How many moles are in 41.6 g
of ammonium carbonate?
n (mol) =
m (g)
M (g/mol)
• divide given mass by mol weight
• what is ammonium carbonate? NH4+ ,CO32– " (NH4)2CO3
• what is its mol. weight?
2!14.01 + 8!1.008 + 12.01 + 3!16.00 = 96.09 g/mol
Sample Problem 3.2
Ammonium carbonate, is a white solid that decomposes with
warming. Among its many uses, it is a component of baking powder,
fire extinguishers, and smelling salts. How many moles are in 41.6 g
of ammonium carbonate?
n (mol) =
m (g)
M (g/mol)
• divide given mass by mol weight
• what is ammonium carbonate? NH4+ ,CO32– " (NH4)2CO3
• what is its mol. weight?
2!14.01 + 8!1.008 + 12.01 + 3!16.00 = 96.09 g/mol
• answer: 41.6 g : 96.06 g/mol = 0.433 mol
Sample Problem 3.2
Ammonium carbonate, is a white solid that decomposes with
warming. Among its many uses, it is a component of baking powder,
fire extinguishers, and smelling salts. How many moles are in 41.6 g
of ammonium carbonate?
n (mol) =
m (g)
M (g/mol)
• divide given mass by mol weight
• what is ammonium carbonate? NH4+ ,CO32– " (NH4)2CO3
• what is its mol. weight?
2!14.01 + 8!1.008 + 12.01 + 3!16.00 = 96.09 g/mol
• answer: 41.6 g : 96.06 g/mol = 0.433 mol
(number of formula units = 0.433 mol ! 6.022!1023 mol-1 = 2.61!1023)
Mass Percent from Chemical
Formula
Glucose (C6H12O6) is the most important nutrient in the living cell
for generating energy. What is the mass percent of each element in
glucose?
• let’s focus on carbon first
Mass Percent from Chemical
Formula
Glucose (C6H12O6) is the most important nutrient in the living cell
for generating energy. What is the mass percent of each element in
glucose?
• let’s focus on carbon first
mass of C in one mole(cule) .
mass of C6H12O6 in one mole(cule)
Mass Percent from Chemical
Formula
Glucose (C6H12O6) is the most important nutrient in the living cell
for generating energy. What is the mass percent of each element in
glucose?
• let’s focus on carbon first
mass of C in one mole(cule) .
mass of C6H12O6 in one mole(cule)
6!12.01
.= 72.06 .
= 0.400 = 40.0 mass%
6!12.01 + 12!1.008 + 6!16.00 180.156
Elemental Analysis and
Molecular Formula
• complete burning, than analysis of oxidation products
• used to determine empirical formula of an unknown
compound (gives an empirical formula only!)
• used to confirm the structure
• (mass spectroscopy is a superior modern technique
that gives a molecular formula directly)
Elemental Analysis and
Molecular Formula
Sample Problem 3.5: During physical activity, lactic acid (M =
90.08 g/mol) forms in muscle and is responsible for muscle
soreness. Elemental analysis shows that it contains 40.0
mass% C, 6.71 mass% H, and 53.3 mass% O.
(a) determine the empirical formula of lactic acid
(b) determine the molecular formula of lactic acid
Elemental Analysis and
Molecular Formula
Sample Problem 3.5: During physical activity, lactic acid (M =
90.08 g/mol) forms in muscle and is responsible for muscle
soreness. Elemental analysis shows that it contains 40.0
mass% C, 6.71 mass% H, and 53.3 mass% O.
(a) determine the empirical formula of lactic acid
(b) determine the molecular formula of lactic acid
• mass% # arbitrary weight (let’s take 100 g)
• convert grams to moles
Elemental Analysis and
Molecular Formula
Sample Problem 3.5: During physical activity, lactic acid (M =
90.08 g/mol) forms in muscle and is responsible for muscle
soreness. Elemental analysis shows that it contains 40.0
mass% C, 6.71 mass% H, and 53.3 mass% O.
(a) determine the empirical formula of lactic acid
(b) determine the molecular formula of lactic acid
• mass% # arbitrary weight (let’s take 100 g)
• convert grams to moles
40.0 g
C=
= 3.33 mol
12.01 g/mol
O=
6.71 g
H=
= 6.66 mol
1.008 g/mol
53.3 g
= 3.33 mol
16.00 g/mol
Elemental Analysis and
Molecular Formula
Sample Problem 3.5: During physical activity, lactic acid (M =
90.08 g/mol) forms in muscle and is responsible for muscle
soreness. Elemental analysis shows that it contains 40.0
mass% C, 6.71 mass% H, and 53.3 mass% O.
(a) determine the empirical formula of lactic acid
(b) determine the molecular formula of lactic acid
• mass% # arbitrary weight (let’s take 100 g)
• convert grams to moles
40.0 g
C=
= 3.33 mol
12.01 g/mol
O=
6.71 g
H=
= 6.66 mol
1.008 g/mol
53.3 g
= 3.33 mol
16.00 g/mol
CH2O
Elemental Analysis and
Molecular Formula
Sample Problem 3.5: During physical activity, lactic acid (M =
90.08 g/mol) forms in muscle and is responsible for muscle
soreness. Elemental analysis shows that it contains 40.0
mass% C, 6.71 mass% H, and 53.3 mass% O.
(a) determine the empirical formula of lactic acid
(b) determine the molecular formula of lactic acid
Empirical formula:
CH2O
"
“M = 30.03 g/mol”
Actual M is 3 (three) times greater, therefore:
Molecular formula:
C3H6O3
Chemical Equations
General Structure:
Starting Material(s) # Product(s)