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Science 1206 Unit 2: Chemical Reactions Pt 1 Page 1 of 23

Introduction to Chemistry and Matter

Chemistry

- The study of matter, its properties, and its changes or transformations

Matter

- Anything that has mass and takes up space, which have both physical and chemical

properties.

Laboratory Safety

TEXT: p. 658-660 (safety skills)

WHMIS

- Workplace Hazard Material Information System

- Developed to standardize the labeling of dangerous materials in all workplaces

http://www.ccohs.ca/oshanswers/chemicals/whmis_ghs/pictograms.html

http://www.ccohs.ca/oshanswers/chemicals/whmis_ghs/pictograms.html


MSDS

- Material Safety Data Sheet

- Each chemical purchased by the school comes with an MSDS. There is a binder

containing all the MSDS in the chemistry lab for easy referral.

- Each data sheet contains 9 categories summarizing chemical properties and safety

measures for each particular chemical.

Chemical Tests

TEXT: p. 173-174 (chemical tests)

p. 290 (indicators, litmus paper, acid/base test)

Chemical tests

- Distinctive chemical reactions to identify unknown gases or other substances.

- There are 7 common chemical tests that you will observe:

o Test for water vapour: Present if colbalt chloride test paper changes from blue to

pink.

o Test for carbon dioxide: Present if limewater solution turns milky when the gas is

bubbled into it

o Test for hydrogen gas: Present if a flaming splint at the mouth of the tube pops.

o Test for oxygen gas: Present if a glowing splint bursts into flame.

o Test for acid: In acid solutions, blue litmus paper turns red

o Test for base: In basic solutions, red litmus paper turns blue

o Test for aqueous solution of a salt: When a salt dissolves in water, it will conduct

electricity under electrolysis.

Physical and Chemical Properties and Changes

TEXT: p. 173 (properties of matter)

Physical property

- A characteristic of a substance

Chemical property

- A characteristic behavior that occurs when a substance changes to a new substance


Physical change

- A change (such as dissolving or melting) in the size or form of a substance, which does

not change the chemical properties of a substance.

Chemical change

- A change in chemical properties.

Formation of Ionic Compounds

TEXT: p. 188-189 (how elements form compounds)

p. 192 (ionic compounds)

Formation of Ions

Remember:

Noble gases have full valence energy levels and are unreactive.

They are not found in compounds in nature.

To become stable and achieve a noble gas configuration,

atoms will lose or gain electrons

to form simple ions (consisting of only 1 charged atom).

- Metals – always lose electrons to achieve the nearest noble gas configuration forming

CATIONS

o Alkali metals will lose 1 electron to become 1+

o Alkaline earth metals will lose 2 electrons to become 2+


- Non-Metals – Always gain electrons to achieve the nearest noble gas configuration

forming ANIONS.

o Halogens gain 1 electron to become 1-

o Group 16 gain 2 electrons to become 2-

o Group 15 gain 3 electrons to become 3-


Ions Forming Compounds

Remember:

Ionic compounds are always formed from a metal and a non-metal

because of the attraction of opposite charges.

Negative cations attract positive anions to form an ionic bond.

When metals and non-metals form compounds the charges attract each other in such a way

that the overall charge for the compound is ZERO.

Example: LiF

Example: LiCl


What about when the charges don’t balance?

MgF2

In addition, to indicate the number of each ion in the compound a subscript is used

(except when there is only 1 ion, and then no subscript is used)

Example: Mg and O forming an ionic bond

Example: Ca and Cl forming an ionic bond


Conclusion: The charges must always balance!

Remember:

To name simple ionic compounds name the metal

and then the non-metal ending in ‘ide’.

Naming Ionic Compounds

TEXT p. 192-194 (ionic compounds)

Step 1:

Write the name of the metallic ion (cation) first.

Step 2:

Write the name of the non-metallic ion (anion) second adding the ‘ide’ ending.

No need to worry about the subscripts here!

Examples

LiBr

CaCl2

Writing Formulas from Names

Step 1:

Determine the chemical symbol for the metallic ion (cation) and ALSO the charge on this ion

(read it from the periodic table).

Step 2:

Determine the chemical symbol for the non-metallic ion (anion) and ALSO the charge on this

ion (you know where to find it!).

Step 3:

Use the Criss Cross Rule to determine the subscripts in the chemical formula (balance the

charges)

DO NOT include the charges in the formula!


Examples

Important Points to Remember!

The subscript 1 is NEVER written (always understood when no subscript is written)

When subscripts are divisible by the same number you must REDUCE them. (remember –

a formula unit is always an empirical formula)


Formation of Molecular Compounds

TEXT: p. 189 (chemical formulas and composition of compounds)

p. 201-202 (molecular compounds)

When Two Non-Metals Bond

Covalent bond

- A shared pair of electrons held between two non-metal atoms that hold the atoms

together in a molecule.

- Non-metal atoms will share electrons to achieve a full valence shell.

Example:

Cl2

Example:

Cl and C


Example:

N and F

Many non-metallic elements exist as covalently bonded molecules – diatomic molecules.

- Rule of 7 (shape of a seven on the periodic table)

o Hydrogen H2

o Nitrogen N2

o Oxygen O2

o Fluorine F2

o Chlorine Cl2

o Bromine Br2

o Iodine I2

- Also:

o Phosphorus P4

o Sulfur S8

Naming Molecular Compounds

TEXT: p. 203-204

Writing Names from Formulas

Step 1:

Identify the first non-metal element in the compound and write the chemical name for it.

Step 2:

Determine the prefix to use for the first element by looking at its subscript and using the table

below:


If there is no subscript then you DO NOT need to use mono- for the first atom in compound!!

Step 3:

Write the name of the second non-metal element in the compound and change the ending to

‘ide’.

Step 4:

Determine the prefix of the second element by looking at its subscript and using the table

below.

Examples

CO2

P4O10

Writing Formulas from Names

Step 1:

Determine the chemical symbol for each element in the compound.

Step 2:

Determine the subscript for each element by looking at the prefix used for each atom.

Examples

Dinitrogen tetraoxide

Carbon monoxide


IONIC COMPOUNDS CONTAINING POLYATOMIC IONS

Writing Formulas from Names (containing polyatomic ions)

TEXT: p. 196-198 (polyatomic ions)

Polyatomic ion - A group of atoms that tend to stay together and carry and overall charge.

- They do not dissociate (separate) when dissolving,

- Common ones are listed on the back of your periodic table (including their charges)

Writing formulas is similar to that for simple ionic compounds.

Step 1: Write the chemical symbols (from the periodic table)

Step 2: Include the charges (from the periodic table)

Step 3: Charges must be balanced to determine subscripts. The Criss Cross Rule can be

used!

However:

When there are 2 or more polyatomic ions in compound,

brackets () must be used to indicate

that the subscript is for the entire polyatomic ion

and not just the last atom of the polyatomic ion.

Examples:


OTHER EXAMPLES:

To Conclude!


Writing Names from Formulas (containing polyatomic ions)

Step 1:

Recognize that a polyatomic ion is involved. You should check the back of your periodic table

for the polyatomic ion. Look carefully!

Step 2:

Name the cation (positive metallic ion).

Step 3:

Name the anion (in this case, the polyatomic ion) – use the ending given in the table.

No need to change it to ‘ide’. Just write it like you see it on the back of the periodic table!!


Writing Formulas from Names (containing multivalent ions) TEXT: p. 195 (atoms with more than one ionic charge)

Multivalent ion

- Some metal atoms can form more than one ion with different charges.

- You will see these possible charges in the top right of an atom’s place in the periodic

table – no need to memorize!

- The specific multivalent ion in a compound will thereby determine the subscripts as

charges must be balanced.

- Example: Copper can form a Cu+ ion or a Cu 2+ ion.

Step 1:

Notice that when a multivalent ion forms a compound the charge of the ion is indicated by a

Roman numeral in brackets after the metal ion – again – no guessing required!

Example: copper (I) oxide

Write the symbol for the cation (metal ion) with the charge (indicated in brackets)

Step 2:

Write the symbol for the anion (non metal ion) and its charge

Step 3:

Use the Criss Cross Rule to balance the charges and determine the subscripts.

Another example:

mercury (II) phosphate

tin (II) carbonate

lead (II) chromate

copper (I) sulfite

iron (III) nitrate

Writing Names from Formulas (containing multivalent ions)

Step 1:

Recognize that there is a multivalent ion in the compound – you can double check with your

periodic table.


Step 2:

Write the symbol for the multivalent cation with BOTH of its charges.

Step 3:

Write the symbol for the anion and its charge.

For this next part you MUST pay attention to the subscripts in the chemical formula!

Step 4:

First, calculate the total negative charge in the compound by multiplying the anion’s charge by

the anion’s subscript.

Step 5:

Next, calculate BOTH total possible positive charges by multiplying the cation’s subscript by the

cation’s charges.

Step 6:

Determine which cation charge balances the total positive charge in the compound.

Step 7:

Write the name of the cation followed by the charge (in Roman Numerals in brackets) and then

the name of the anion.


As in ALL ionic compounds:

The positive and negative charges must ALWAYS balance.

Examples:

Cu2S

HgF2

Sn(NO3)2

FePO4

Ni(CH3COO)2


Writing Names from Formulas (Hydrates)

TEXT: p. 236 (definition)

Hydrate

- A solid compound that contains water molecules as a part of the solid crystalline

structure.

Naming a hydrate involves 2 steps:

Step 1:

Name the ionic part following all the same rules previously learned.

Step 2:

Indicate the number of water molecules using the same prefixes as for molecular compounds.

Attach the prefix to the word ‘hydrate’.


Acids and Bases

TEXT p. 288-290 (acids and bases)

p. 293-294 (properties of acids and bases)

p. 295 (formulas for acids and bases)

Acids

- Special hydrogen containing compounds that undergo ionization when dissolved in

water to produce H+ ions.

Some everyday acids:

- Lemon juice

- Vinegar

- Vitamin C (ascorbic acid)

- Battery acid

Properties of acids:

- Highly reactive with metals to produce hydrogen gas - H2(g)

- Sour tasting (Never taste anything in the lab!)

- May be solid, liquid or gas at room temperature

- Soluble in water (like ionic compounds)

- Form electrolytic solutions (conduct electricity - they are electrolytes)

- Form solutions that turn blue litmus paper to red (B RA)


Writing Acid Names form Formulas (and vice versa)

Generally acidic compounds are named as ionic compounds AND

converted to the acid name according to the following:

3 Acid Naming Rules Rule #1: hydrogen ________ide becomes hydro______ic acid

Acid formula ionic name would be acid name

ex: HCl(aq) hydrogen chloride hydrochloric acid

1. _____________________ hydrogen bromide _______________________

2. HCN(aq) __________________________ _______________________

3. _____________________ __________________________ hydrofluoric acid

Rule #2: hydrogen________ate becomes ________ic acid


ex: HClO3(aq) hydrogen chlorate chloric acid

1. _____________________ hydrogen borate _______________________

2. HNO3(aq) __________________________ _______________________

3. _____________________ __________________________ permanganic acid

Rule #3: hydrogen________ite becomes ________ous acid


ex: HNO2(aq) hydrogen nitrite nitrous acid

1. _____________________ hydrogen chlorite ________________________

2. HClO(aq) ___________________________ ________________________

3. _____________________ ___________________________ sulfurous acid

NOTE:

when naming acids with the root words “sulf” and “phosph”, extra syllables are added to make them sound better.

Add “ur” to “sulf” and add “or” to “phosph”. therefore H2SO4(aq) is sulfuric acid NOT sulfic acid

and H3PO4(aq) is phosphoric acid NOT phosphic acid

Homework - WS Naming Acids


Bases

- A group of compounds that dissolve (dissociate) in water to produce hydroxide ions

(OH-)

Some everyday bases:

- Ammonia

- Baking soda

- Drain cleaner

- Soap

- Bleach

Properties of bases:

- Taste bitter (again – DON’T taste anything in the lab!)

- Soluble in water

- Form electrolytic solutions (conduct electricity – they are electrolytes)

- Feel slippery in solution

- React with proteins to break them down into smaller molecules

- May also be described as alkaline

- Form solutions that turn red litmus paper blue (RB)

Writing Names and Formulas for Bases

A base is an ionic compound that contains the hydroxide ion (on the back of your

periodic table)

Naming and formula writing will follow all the rules for ionic compounds and polyatomic

ions.

Examples:

NaOH calcium hydroxide

Mg(OH)2 potassium hydroxide

LiOH beryllium hydroxide


When Acids and Bases are Mixed

TEXT p. 314 (reacting acids and bases)

p. 317-319 (neutralization reactions)

Neutralization reaction

- Mixing an acid with a base (or vice versa)

to temper (reduce) the effects of one or the other

- Products are water and a salt

A Salt

- An ionic compound that will conduct electricity when dissolved in water (aqueous).

- BTW – salts do NOT change the color of litmus paper!

Generalized neutralization reaction:

Acid + Base water + a salt

Better yet:

Hydrochloric acid + sodium hydroxide water + sodium chloride

Applications of Neutralizations Reactions:

- Using lemon juice (acidic) to eliminate fish odors (basic)

- Using Tums (basic) for heartburn (acidic)

- Baking with baking soda (basic) and an acid (like lemon juice or sour cream) to make

your cakes rise

- Cleaning up acid spills in the lab with baking soda (base)


pH Scale

TEXT p. 296 (pH scale)

pH Scale

- A scale from 1 to 14 used to measure acidity, alkalinity or neutrality.

- pH < 7 acidic

- pH = 7 neutral (neither acidic or basic)

- pH > 7 alkaline (basic)

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