CH1000 Fundament als of Chemistry Module 2 – Chapter 6

Common and Systematic Names

• Chemical nomenclature is the systematic naming of chemical compounds

• Common names are historical names of compounds which are not based on systematic rules

• Common names are often used because systematic names are too long and technical for everyday use

• Chemists prefer systematic names that precisely identify the chemical composition of compounds.

• Example CaO • Common name: lime

• Systematic name: calcium oxide

Naming Flowchart

We will focus on nomenclature of inorganic compounds

Elements and Ions

• The formula for most elements is the symbol of the element off of the periodic table.

• Diatomic molecules are an exception:

• Two other elements also exist in polyatomic arrangements:

Naming Anions

•Remember from Chapter 5 that any neutral atom that gains an electron is called an anion

•When naming anions, change the element ending to -ide

Symbols of the Elements •Each element has an abbreviation called a symbol.

•The first letter of a symbol must always be capitalized.

•If a second letter is needed, it should be lowercase.

Predicting Ion Charge from Periodic Table

•Metals form cations

•The positive charge is equal to the group number

Predicting Ion Charge from Periodic Table

•Nonmetals form anions

•The negative charge is equal to 8 – the group number

Writing Formulas from Names of Ionic Compounds

•Ionic compounds contain both a cation and an anion.

•Ionic compounds must have a net charge of 0

•The sum of charges of the cations and anions in an ionic compound equal 0

•Rules for writing formulas for ionic compounds: • Write the metal ion followed by the

nonmetal ion formula

• Combine the smallest whole numbers of each ion to provide an overall charge equal to zero

• Write the compound formula for the metal and nonmetal, using subscripts determined from Step 2 for each ion

Naming Ionic Binary Compounds

•Binary compounds containing a metal which forms only one cation

•By convention, the cation is written/named first followed by the anion

•Rules for naming binary ionic compounds:

• Name the cation • Write the anion root and

add the –ide suffix

Naming Compounds Containing Metals with

Multiple Charges

•Rules for Naming Compounds Involving Metals that Could Form Multiple Charges

• Write the cation name.

• Write the cation charge in Roman numerals in parentheses.

• Write the root of the anion and use the –ide suffix.

•Exception: for metals that only form two cations, a Latin root with either an –ous or –ic suffix can also be used.

Formula Name Classical Name Formula Name Classical Name

Cu+ Copper(I) cuprous Sn2+ Tin(II) stannous

Cu2+ Copper(II) cupric Sn4+ Tin(IV) stannic

Fe2+ Iron(II) ferrous Pb2+ Lead(II) plumbous

Fe3+ Iron(III) ferric Pb4+ Lead(IV) plumbic

Naming Molecular Compounds

•Molecular compounds contain two nonmetals

•Rules for naming molecular compounds: • Write the name for the first element, including the appropriate prefix

(mono is rarely used). • Write the name for the second element, including the appropriate prefix

and -ide ending (mono is used for the 2nd element).

Prefix Number Prefix Number

mono 1 hexa 6

di 2 hepta 7

tri 3 octa 8

tetra 4 nona 9

penta 5 deca 10

Naming Binary Acids

Rules for naming Binary Acids:

Write the prefix hydro followed by the root of the second element and add an –ic suffix

Add the word acid

Hydrogen is always written first in an acid formula.

This is the indicator that it is an acid

Certain binary compounds containing hydrogen behave as acids in water and have special names.

HCl(g) is hydrogen chloride HCl(aq) is hydrochloric acid

Naming Polyatomic Ions

•A polyatomic ion is anion that contains two or more elements

•The names, formulas and charges of common polyatomic ions should be learned.

•Rules for naming compounds containing polyatomic ions • Name the cation • Name the anion

Name Formula Charge Name Formula Charge

Acetate C2H3O2 - -1 Cyanide CN- -1

Ammonium NH4 + +1 Dichromate Cr2O7

2- -2

Hydrogen Carbonate

HCO3 - -1 Hydroxide OH- -1

Hydrogen Sulfate

HSO4 - -1 Nitrate NO3

- -1

Bromate BrO3 - -1 Nitrite NO2

- -1

Carbonate CO3 2- -2 Permanganate MnO4

- -1

Chlorate ClO3 - -1 Phosphate PO4

3- -3

Chromate CrO4 2- -2 Sulfate SO4

2- -2

Sulfite SO3 2- -2

Naming Oxyanions

•Oxyanions are polyatomic ions that contain oxygen

•Often end in suffix –ate or –ite

•-ate compounds contain more O atoms than ite compound(s)

•For elements that form multiple ions with oxygen, prefixes are also needed: • Per: add one oxygen to the –ate root • Hypo – subtract one oxygen from the –

ite root

Anion Formula

Anion Name Anion

Formula Anion Name

ClO- hypochlorite HClO hypochlorous

acid

ClO2 - chlorite HClO2 chlorous acid

ClO3 - chlorate HClO3 chloric acid

ClO4 - perchlorate HClO4 perchloric acid

More Complicated Polyatomics

•Inorganic ions can be formed from more than 3 elements

•The same method is used as before: • Identify the ions and name in order • Cations before anions

Compound Ions Name

NaHCO3 Na +; HCO3

- Sodium hydrogen carbonate

NaHS Na+; HS- Sodium hydrogen

sulfide

MgNH4PO4 Mg2+; NH4

+; PO4

3-

Magnesium ammonium phosphate

NaKSO4 Na +; K+; SO4

2- Sodium potassium sulfate

Naming Acids

• Acids generally begin with hydrogen • To recognize oxyacids, make sure: • H is the first element in the formula • The compound contains a polyatomic ion with oxygen

• The following modifications are made to the name of the acid: • -ate ions are changed to –ic acids • -ite ions are changed to –ous acids • -ic acids contain one more oxygen than –ous acids

Naming Acids Flowchart

Reading Review

What type of ions do metals form?

What type of ions do nonmetals form?

What is the chemical formula for potassium sulfide?

Name the compound CrCl3.

Acids often begin with what element?

CH1000 Fundament als of Chemistry Module 2 – Chapter 8

Chemical Equations

• Chemists use chemical equations to: • Summarize a chemical reaction by displaying the substances reacting and

forming. • Indicate specific amounts of materials consumed or produced during the

reaction.

• Reactants: substances consumed during the reaction.

• Products: substances formed during the reaction.

• Atom balance must be maintained in all chemical reactions.

• All atoms from reactants must appear as part of products.

a A + b B c C + d D

The coefficient 1 is not written in a balanced equation.

Chemical Equations

1. Reactants and products are separated by an arrow.

2. Reactants are on the left side of the arrow, products are on the right.

3. Whole number coefficients are placed in front of substances to balance the atoms in the equation.

4. The numbers indicate the units of the substance reacted or formed during the reaction.

5. Information about the reaction (temperature, time) may be placed above or below the reaction arrow.

6. The physical state is written in brackets after the formula of the substance. (g) for gas, (l) for liquid, (s) for solid, (aq) for aqueous

a A + b B c C + d D

Reactant s

Products

Symbol Summary

Symbol Significance

Produces (points towards products)

(s) Solid (written after substance)

(l) Liquid (written after substance)

(g) Gas (written after substance)

(aq) Substance dissolved in an aqueous solution

Heat is added (above or below reaction arrow)

Δ

Law of Conservation of Mass

• The total mass of substances in a chemical reaction must remain constant.

water hydrogen + oxygen

100.0 g 11.2 g 88.8 g

100.0 g total of productsreactants

In any chemical reaction: Mass of reactants = Mass of products

Writing and Balancing Chemical Equations

A balanced chemical equations contain the same number of each kind of atom on both sides of the equation.

1. Write a word equation for the reaction.

2. Write the correct formula for each substance (unbalanced):

3. Balance the equation a) Count the number of each atom on the reactants and

products side and determine what requires balancing.

b) Balance each element sequentially, using whole numbers. It is often best to balance metals first.

mercury(II) oxide mercury + oxygen Δ

HgO Hg + O2 Δ

Hg: 1 O: 1

Hg: 1 O: 2

HgO Hg + O2 Δ

Oxygen atoms need balancing on the reactants side.

2 HgO Hg + O2 Δ

Hg: 2 O: 2

Hg: 1 O: 2

Now Hg atoms need balancing on the products side.

Writing and Balancing Chemical Equations

4. Check after adding coefficients that all atoms still balance. Adjust as needed (a 2 is needed in front of Hg).

5. Do a final check to make sure all atoms now balance on both sides of the equation.

2 HgO 2 Hg + O2 Δ

Hg: 2 O: 2

Hg: 2 O: 2

Note: always use the smallest whole numbers!

4 HgO 4 Hg + 2 O2 Δ

Balanced but incorrect form!

Information in a Chemical Equation

© 2014 John Wiley & Sons, Inc. All rights reserved.

Information from a Chemical Equation

• From the chemical equation below, how many moles of oxygen are needed to burn 2 molecules of propane (C3H8)?

• a) 5 molecules of oxygen

• b) 6 molecules of oxygen

• c) 10 molecules of oxygen

• d) 15 molecules of oxygen

C3H8 + 5 O2 3 CO2 + 4 H2O

For every 1 molecule of propane, 5 molecules of O2 are needed to fully

react. Two molecules of propane would then

require 2 x 5 = 10 molecules of oxygen.

Types of Chemical Equations

1. Combination reactions 2. Decomposition reactions 3. Single displacement reactions 4. Double displacement reactions 5. Oxidation-reduction (redox) reactions

(Chapter 17)

Reactions are classified into subtypes to aide in predicting

the products of chemical reactions.

Reactions are classified into five major categories:

Combination Reactions Two reactants combine to give a single product.

A + B AB

Decomposition Reactions

A single reactant breaks down (decomposes) into two or more products

AB A + B

Single Displacement Reactions

One element (A) reacts with a compound (BC) to replace

one element in the compound, giving a new element (B)

and a different compound (AC).

General Types of Single Displacement Reactions

Double Displacement Reactions

Two compounds exchange partners with one another to yield two new compounds.

AB + CD AD + CB

General Types of Double Displacement Reactions

Double Displacement Reactions

Two compounds exchange partners with one another to yield two new compounds.

AB + CD AD + CB

General Types of Double Displacement Reactions Writing Reaction Equations Practice

1. Write the reaction equation between aqueous solution of hydroiodic acid and sodium hydroxide.

2. First convert names to chemical formulas and determine the type of reaction.

HI (acid)/NaOH(base)

Neutralization Reaction acid + base salt + water HI (aq) + NaOH (aq) NaI (aq) + H2O (l) Salt formula must charge balance (Na+ and I–)

Heat in Chemical Reactions

Terminology

Energy transfer and changes accompany any chemical reaction

Heat of reaction: quantity of heat actually produced during a chemical reaction. Units: kilojoules (kJ) or kilocalories (kcal)

Exothermic reactions: release heat. H2 (g) + Cl2 (g) 2 HCl (g) + 185 kJ Heat can be treated as a product

Endothermic reactions: absorb heat. N2 (g) + O2 (g) + 181 kJ 2 NO (g) Heat can be treated as a product

C (s) + O2 (g) CO2 (g) + 393 kJ

1 mol of C reacts with 1 mol of O2 to provide 1 mol of CO2 and 393 kJ of heat are released.

Heat in Chemical Reactions Equations Practice

Heat as an Energy Transfer

Vehicle in Nature

Graphical Representations of

Endothermic Reactions

•Products are at a higher potential energy than reactants. •Activation energy: Amount of energy needed to initiate a chemical reaction.

Reaction Coordinate Diagram

Graphical Representations of

Exothermic Reactions

•Products are at a lower potential energy than reactants. •Activation energy: Amount of energy needed to initiate a chemical reaction.

Reaction Coordinate Diagram

Reading Review

How do you know if a reaction is a combustion reaction?

What is an endothermic reaction?

What is an exothermic reaction?

What are the four types of chemical equations?.

How do you know if an equation is balanced?

CH1000 Fundament als of Chemistry Module 2 – Chapter 7

The Mole (or mol)

• In chemistry, a mole (mol) is a standard scientific unit for measuring large quantities of very small entities such as atoms, molecules, or other specified particles.

• The number represented by 1 mole above is also called Avogadro’s number.

• 1 mol of any element contains the same number of atoms, but can vary greatly in the overall mass. (Atoms of different elements have different masses)

Molar Mass

•Molar Mass is the atomic mass of an element or compound in grams which contains Avogadro’s number of particles • Molar masses are expressed

to 4 significant figures in the text

•Convert atomic mass units on the periodic table to grams and sum the masses of the total atoms present

Mole Map ** Not found in the textbook,

save for easy access

Molar Mass of Compounds

•Much like an element, molar mass can be defined for a compound •Molar Mass is the mass of one mole of the formula unit of a compound • The molar mass of a

compound is equal to the sum of the molar masses of all the atoms in the molecule

Percent Composition of Compounds

Percent composition is the mass percent of each element in a compound. • Percent = parts per 100 parts • Molar mass is the total mass (100%) of the compound

% Composition is independent of sample size

% Composition can be determined by:

• 1. Knowing the compound’s formula • 2. Using experimental data

Percent Composition from the Compound’s Formula

Percent Composition from Experimental Data

Empirical and Molecular Formula

Empirical Formula Smallest whole number ratio of atoms in a compound

Molecular Formula Actual formula of a compound. Represents the total number of atoms in one formula unit of the compound

Calculating Empirical Formulas •Special Case: • If fractions are

encountered, multiply by a common factor to provide whole numbers for each subscript.

Calculating the Molecular Formula from the Empirical Formula

•If molar mass is known, the molecular formula can be calculated from the empirical formula •Molecular formula is a multiple of the empirical formula.

Reading Review

What is Avagadro’s number?

How would you convert from grams

to atoms of an element?

What is a mole?

What is the difference between

empirical and molecular formulas?

What is the special case when

calculating empirical formulas?

CH1000 Fundament als of Chemistry Module 2 – Chapter 9

Introduction to Stoichiometry

• Equations must always be balanced before calculation of any mass, moles, or volume of a reactant or product!

• Stoichiometry is the area of chemistry that deals with quantitative relationships between products and reactants in chemical equations.

• Solving stoichiometry problems always requires the use of: • A balanced chemical equation (coefficients must be known!) • Conversion factors in units of moles (mole ratios)

Mole Ratios

•Mole ratio is the conversion factor between any two species in a chemical reaction

•The mole ratio will come from the coefficients of a balanced chemical equation

Mole Ratios in Practice

•The mole ratio can be used as a conversion factor to convert between moles of one substance and another.

•The desired quantity goes in the numerator and the known quantity goes into the denominator of the mole ratio

•Same method as the solution map from chapter 2.

Problem Solving for Stoichiometry Problems

Problem Solving for Stoichiometry Problems

Problem Solving for Stoichiometry

Problems

•Remember that Step 1 is to always ensure you have a balanced equation!!!

•You must be in moles to convert from one substance to another!

Limiting Reactants •In chemical reactions, the reaction will occur until one of the reactants runs out

•Think of a burning fire. You need oxygen, heat and fuel to keep a fire going. If the fuel (wood) all burns, the fire goes out. The wood would be the limiting reactant because had it not all burned, the fire would continue to exist.

•In a chemical reaction, the maximum amount of product formed depends on the amount of reactant not in excess, the limiting reactant

Reaction Yield

• The amount of products formed calculated by stoichiometry are the maximum yields possible (100%)

• Yields are often lower in practice due to side reactions, loss of product while isolating/transferring the material, etc.

• The theoretical yield is the maximum possible yield for a reaction, calculated based on the balanced chemical equation.

• The actual yield is the yield obtained from the reaction

• The percent yield is the ratio of the actual and theoretical yield

Reading Review

What is stoichiometry?

What unit must you be in to convert from one substance to another?

What is the limiting reactant?

What is the difference between theoretical and actual yields?

How do you calculate the percent yield?