FORMULAS & EQUATIONS

Topic 1 – Introduction to Formulas 2 H 2 O 2  2 H 2 O + O 2 What information can we get from this equation?

1. INTRO: You already know that chemical symbols are used to represent different elements Ex: H = Hydrogen, Na = Sodium. Now you will see how these different symbols can be combined to form the formulas of different compounds.

2. Symbols are used to represent elements. Ex: Cl for Chlorine and O for oxygen Diatomic molecules are symbols that have subscripts. Ex: Cl 2 and O 2

Anytime there is a subscript in a formula, it indicates the number of atoms present. Ex: Cl 2 has ______ chlorine atoms. Ex: a molecule of H 2 SO 4 has …. ____ hydrogen atoms ____ sulfur atom _____oxygen atoms.

3. FORMULAS 3. FORMULAS give both quantitative and qualitative data. A. Qualitative data is data that cannot be measured Ex: the man is TALL; it is COLD outside today! Ex: The formula CO 2 contains Carbon and Oxygen

B. Quantitative data gives actual numbers (or QUANTITIES) Ex: The man is 6’8”; It is 2ºF outside today! Ex: The formula CO 2 contains 1 Carbon atom and 2 Oxygen atoms.

4. TYPES OF FORMULAS A.EMPIRICAL FORMULA - shows the formula in its simplest integer ratio B. MOLECULAR FORMULA - shows the actual ratios found in nature - may also be the same as the empirical but not necessarily

Ex: C 6 H 12 O 6 is a molecular formula. The empirical formula would be CH 2 O. Ex: N 2 O 2 is a molecular formula. It can be simplified into the empirical formula NO.

4. COEFFICIENTS A coefficient (number written in front of the entire formula) represents how many units of the formula are present in a given sample. Ex: 2H 2 O means that there are two water molecules present.

To figure out how many atoms are present, multiply each value by the coefficient. Ex: 2CH 4 There are ____ Carbon atoms present, and _____ Hydrogen atoms present.

5. PARENTHESIS If there is a subscript outside of parenthesis, it applies only to the atoms in the parenthesis; not to any element before or after it. For example: Ca(OH) 2 means that there is __ Calcium, __ Oxygen, and __ hydrogen.

Ex: How many atoms of each element in: 1. Na(NH 3 ) 2 1 Sodium 2 Nitrogen6 Hydrogen TOTAL = 9 atoms 2.Al(OH) 3 1 Aluminum3 Oxygen3 Hydrogen TOTAL = 7 atoms 3. 3Al(OH) 3 3 Aluminum9 Oxygen9 Hydrogen TOTAL = 21 atoms

Topic 2 – Writing Formulas All compounds must be electrically neutral. The sum of the charges of all the atoms must equal zero.

Topic 2 – Writing Formulas 1. Writing Ionic Formulas Look up the oxidation numbers of Na and Cl Since Na is ___and Cl is ___, you only need one of each to be neutral. The formula is written _________.

Topic 2 – Writing Formulas Look up the oxidation number of Magnesium and Oxygen: Mg is ___and O is ___, so you only need one of each to be neutral. The formula is written ________.

Topic 2 – Writing Formulas What about Na and O? Na is ____and Oxygen is ____. Therefore you need ____ sodium atoms to neutralize the one oxygen atom. The formula is written _________.

Topic 2 – Writing Formulas Write the formula for Magnesium and chlorine. Mg is ____Cl is ____ Two chlorines are needed to neutralize one magnesium. The formula is written MgCl 2

Topic 2 – Writing Formulas Criss-Cross Method The oxidation number of each atom will become the subscript of the opposite atom. Reduce to lowest denominator if necessary.

Ex: Barium fluoride

Topic 2 – Writing Formulas Ex: Aluminum Oxide

Topic 2 – Writing Formulas If a metal has more than one oxidation number, a roman numeral will represent the appropriate number to use. This may look confusing, but if there is a roman numeral, then you don’t even need to use the reference table!

Topic 2 – Writing Formulas Ex: Iron (II) Chloride Ex: Iron (III) Chloride

Topic 2 – Writing Formulas 2. Writing Covalent Formulas Covalent molecules (nonmetals) will use prefixes to tell you how many of each to write. Mono = 1 Di = 2 Tri = 3 Tetra = 4

Topic 2 – Writing Formulas Carbon Dioxide CO 2

Topic 2 – Writing Formulas Carbon Tetrafluoride CF 4

Topic 2 – Writing Formulas Dinitrogen Dioxide N 2 O 2

Topic 2 – Writing Formulas 3. Writing Formulas with Polyatomic Ions Look at Table E What is the symbol for: –Hydroxide _______ –Sulfate _________

Topic 2 – Writing Formulas Use the same criss cross method, but put the polyatomic ion in parenthesis if needed: Ex: Calcium Hydroxide

Topic 2 – Writing Formulas Magnesium Phosphate Hydrogen Nitrate

Topic 3 – Naming Compounds TWO TYPES OF COMPOUNDS: Ionic (a metal and a non-metal) Covalent (Molecular) ( 2 non-metals)

Topic 3 – Naming Compounds 1. IONIC A. BINARY IONIC COMPOUNDS -The term “binary ionic” means that there are only two elements involved. Let’s combine Potassium and Chlorine (K and Cl) The positive ion (usually the metal) is placed first. In this example, ____ is placed first and ____ second.Ex: _________

Topic 3 – Naming Compounds The name begins with the name of the first element. In KCl, the name would begin with “_Potassium_.” Next, the name of the second element is changed to end in “ide”. In this example, KCl would then be named “Potassium chloride.”

Topic 3 – Naming Compounds Try these examples: 1. NaCl_____________________ 2. MgS_______________________ 3. ScN ______________________

Topic 3 – Naming Compounds B. POLYATOMIC IONIC COMPOUNDS The term “polyatomic” means several atoms bonded together. A list of common polyatomic ions is found in Table E of your Reference Table. Let’s combine NO 3 and Na.

Topic 3 – Naming Compounds Again, the positive ion is placed first. In this example, _____ is placed first and _________ is placed second.Ex: ______________. The name begins with the name of the first element. In NaNO3, the name would begin with “_____________” The name ends with the name of the polyatomic ion. In NaNO3, the name would be “_________________________________.”

Topic 3 – Naming Compounds ** If there are two polyatomic ions, put the positive one first, and the name of the compound is the name of the two ions. Ex: NH 4 NO 3 is named “Ammonium Nitrate.” Try these examples: 1. KOH _________________________ 2.MgCO 3 ________________________ 3. NH 4 CN _______________________

Topic 3 – Naming Compounds 2. COVALENT (MOLECULAR) COMPOUNDS Reminder: Covalent molecules consist of all NON-METALS Let’s combine Nitrogen (N) and Oxygen (O 2 ) The element with the lower electronegativity is written first. In this example, ____ is written first. Ex: ___________.

COMMON PREFIXES NUMBER OF ATOMSPREFIX 1mono- 2di- 3tri- 4tetra- 5penta- 6hexa- 7hepta- 8octa-

Topic 3 – Naming Compounds The name begins with the name of the first element. In this example, the name starts with “_____________________” For the second part of the name, the name of the second element is changed to end in “ide.” Ex: ______________. You then look at the NUMBER of atoms in each element and add the appropriate prefix. For NO 2, there are 2 oxygen atoms so the name becomes “ Nitrogen Dioxide”

Topic 3 – Naming Compounds Try these examples: HCl _______________________ CO_______________________ CO 2 ___________________________ CH 4 ___________________________ N 2 O 2 ___________________________ SF 6 _________________________

Topic 3 – Naming Compounds

Topic 4– Balancing Equations 1. Conservation of mass In a chemical reaction, the total number of atoms on the reactant side must equal the total number of atoms on the product side. In order to make a reaction “balanced”, we add coefficients to molecules until an equal number of atoms is achieved.

Topic 4– Balancing Equations __H 2 + __O 2  __H 2 O List the amount of each atom on each side: Add coefficients as necessary to balance the equation.

Topic 4– Balancing Equations __H 2 + __Cl 2  __HCl

Topic 4– Balancing Equations __H 2 + __N 2  __NH 3

Topic 4– Balancing Equations __Zn + HCl  __ZnCl 2 + __H 2

Topic 4– Balancing Equations If there is a polyatomic ion in the equation, it is easier to count it as one whole unit. __Ba(NO 3 ) 2 + __Na 2 SO 4  __NaNO 3 + __BaSO 4

Topic 4– Balancing Equations __Pb(NO 3 ) 2 + __KI  __KNO 3 + __PbI 2

Topic 4– Balancing Equations Practice, practice, practice…

Topic 5– Synthesis and Decomposition Synthesis: The combination of one or more elements to form a compound General Formula: A + B  AB Ex: __H 2 +__ O 2  __H 2 O Ex: CO 2 + H 2 O  H 2 CO 3

Synthesis

Topic 5– Synthesis and Decomposition Decomposition is the opposite of synthesis.

Topic 5– Synthesis and Decomposition Decomposition: When a single compound breaks down into more than one product. General formula: AB  A + B Ex: __H 2 O  __H 2 +__ O 2 Ex: H 2 CO 3  CO 2 + H 2 O

Decomposition

Topic 6– Single Replacement Single Replacement = A reaction where one element replaces another element in a compound.

Topic 6– Single Replacement Demonstration Reaction: _Cu + __AgNO 3  __Cu(NO 3 ) 2 + __Ag Record observations:

Topic 6– Single Replacement The general equation for single replacement is: A + BC  B + AC

Topic 6– Single Replacement A single replacement reaction will occur if the element doing the replacing is more reactive than the element being replaced. Metals replace metals Nonmetals replace nonmetals

Topic 6– Single Replacement In the demonstration reaction, would the reverse reaction occur? No! Silver will not react with copper nitrate.

Topic 6– Single Replacement How can I tell if a reaction will occur or not???? Look at Table J Table J shows the reactivity of metals and nonmetals.

Topic 6– Single Replacement An element on Table J reacts with a compound of an element below it. Think of it as element mafia.

Topic 6– Single Replacement State if the following reactions will or will not react and explain why. If they will react, write out the products: A) Zn + Cu(NO 3 ) 2 

Topic 6– Single Replacement B) Cu + Zn(NO 3 ) 2  C) Cl 2 + NaF  D) F 2 + 2NaCl 

Topic 6– Single Replacement

** Any element on Table J can replace any element below it.

Topic 7 – Double Replacement Double replacement reactions occur between two ionic compounds that react in solution (aq) to produce one of three things: A precipitate (insoluble solid) A gas Water

Topic 7 – Double Replacement The general equation for double replacement is: AB + CD  AC + BD Example:

Topic 7 – Double Replacement Reminder: Just as not all single replacement reactions occur, not all double replacement reactions occur. How to tell if a double replacement reaction will occur:

Topic 7 – Double Replacement 1. The reaction will occur if one of the products is a precipitate. A precipitate is an insoluble solid that is not part of the solution. Use Table F to determine if a precipitate will form.

Topic 7 – Double Replacement Soluble or Insoluble?? NaCl _______________ HClO3 _________________ CaBr2 __________________ PbI2 ___________________ Ca(OH)2 __________________ CaCO3 _____________________

Topic 7 – Double Replacement A. Ex: AgNO 3(aq) + NaCl (aq)  ______ + _______

Topic 7 – Double Replacement 2. The reaction will occur if one of the products is a gas. –Na 2 S (aq) + 2HCl (aq)  H 2 S (g) + 2NaCl (aq)

Topic 7 – Double Replacement 3. The reaction will occur if a molecular substance, such as water is formed. NaOH (aq) + HCl(aq)  ______ + ____

Topic 7 – Double Replacement