Stoichiometry. Chapter 9, 10, & 11

Stoichiometry.Stoichiometry.Chapter 9, 10, & 11Chapter 9, 10, & 11

Standard 3Standard 3

Ms. SiddallMs. Siddall

vocabularyvocabulary

1.1. CompoundCompound2.2. Chemical formulaChemical formula3.3. CoefficientCoefficient4.4. StoichiometryStoichiometry5.5. MoleMole6.6. Molar massMolar mass7.7. Molar volumeMolar volume8.8. Avogadro’s numberAvogadro’s number9.9. Standard temperature and pressureStandard temperature and pressure

Anatomy of a chemical formulaAnatomy of a chemical formula

CuSOCuSO4(aq)4(aq)

Atomic symbols describe the type of atoms in the compound

(copper, sulfur, oxygen)subscript numbers describe the number of atoms in the compound

(1 copper, 1 sulfur, 4 oxygen)physical state of the compound is described using subscript letters

(aq = aqueous)

chemical formulachemical formula: : a combination of symbols a combination of symbols and numbers that describe the amount and and numbers that describe the amount and type of atoms that form a compound.type of atoms that form a compound.

Example:

study question 1study question 1

NaNa22OO(s)(s)

In the above formula:In the above formula:

1.1. How many sodium atoms?How many sodium atoms?

2.2. How many oxygen atoms?How many oxygen atoms?

3.3. What is the physical state?What is the physical state?

4.4. Is the compound ionic or covalent?Is the compound ionic or covalent?

An equation describes a chemical An equation describes a chemical reaction or a physical changereaction or a physical change

ReactantsReactants: chemicals that react: chemicals that react ProductsProducts: chemicals that are formed: chemicals that are formed e.xe.x. sodium + oxygen . sodium + oxygen sodium sodium

oxideoxideNa(s) + O2(g) Na2O(s)

reactants product

Standard 3a: describing chemical reactions


Pb(NOPb(NO33))3(aq)3(aq) + KI + KI(aq)(aq) KNO KNO3(aq)3(aq) + PbI + PbI3(s)3(s)

1.1. Label the reactants and the products in the Label the reactants and the products in the reaction abovereaction above

2.2. Are the reactants and products covalent or Are the reactants and products covalent or ionic?ionic?

3.3. How many oxygen atoms are in the compound How many oxygen atoms are in the compound Pb(NOPb(NO33))33? ?

Symbols describing chemical Symbols describing chemical reactionsreactions

Copy table 11.1 (page 323)That’s right – open your book to page 323 and copy that table into your notes… go on… do it! This spot had better not be blank when I check your notebook!


1.1. What do the following symbols What do the following symbols mean?mean?

(l)(l) (aq)(aq)

2.2. Pb(NOPb(NO33))3(aq)3(aq) + KI + KI(aq)(aq) KNO KNO3(aq)3(aq) + PbI + PbI3(s)3(s)

Which compound is solid?Which compound is solid?

The Law of Conservation of Matter:The Law of Conservation of Matter: Matter cannot be created or destroyed.

For chemical equations: The total number of each type of atom must be the same before and after the reaction

Law:Law:Thou shall not Thou shall not

create or create or destroy matterdestroy matter

Balancing chemical equations

exampleexample Sodium reacts with oxygen to Sodium reacts with oxygen to

produce sodium oxideproduce sodium oxide

How many sodium atoms react?How many sodium atoms react? How many sodium atoms are in the How many sodium atoms are in the

product?product? This violates the law of conservation This violates the law of conservation

of matter!of matter!

Na(s) + O2(g) Na2O(s)

1

2


NaINaI(s)(s) + Cl + Cl2(g)2(g) NaCl NaCl(s)(s) + I + I2(s)2(s)

Count the number Count the number of atoms on the of atoms on the reactants sidereactants side

Sodium ____Sodium ____Iodine ____Iodine ____Chlorine ____Chlorine ____

Count the number Count the number of atoms on the of atoms on the products sideproducts side

Sodium ____Sodium ____Iodine ____Iodine ____Chlorine ____Chlorine ____

Does this equation obey the law of conservation of matter?

Coefficients are used to balance the equation number of atoms or formulas needed in

the reaction. These apply to the entire formula (all the atoms)

4Na = 4 sodium atoms 2Na2O = 4 sodium atoms and 2 oxygen atoms

Example: Na(s) + O2(g) Na2O(s)

SUBSCRIPTS CAN NOT CHANGE!SUBSCRIPTS CAN NOT CHANGE!

24

study question 5study question 52Cu(s) + O2(g) 2CuO(s)

Count the number Count the number of atoms on the of atoms on the reactants sidereactants side

copper ____copper ____Oxygen ____Oxygen ____

Count the number Count the number of atoms on the of atoms on the products sideproducts side

copper ____copper ____Oxygen ____Oxygen ____

Does this equation obey the law of conservation of matter?

Rules of Balancing EquationsRules of Balancing Equations

1.1. WriteWrite the equation using the equation using correct formulas. correct formulas. You may You may NOTNOT change the formula in change the formula in any way.any way.

2.2. BalanceBalance the equation using the equation using coefficientscoefficients

Take atomic inventory: (you Take atomic inventory: (you mustmust obey the obey the Law of Conservation of Matter)Law of Conservation of Matter)

Na + O2 Na2O

Reactants:Na1

O2

Products:Na2

O1

Problem: begin with 2 oxygen atoms but end with only 1 This breaks the law of conservation of matter.

Balancing example: sodium and oxygen react to form sodium oxide

Na + O2 Na2O2

solution: Add the coefficient ‘2’ in front of Na2O

Problem: begin with 1 sodium atom but end with 4.This breaks the law of conservation of matter.

Take atomic inventory again:

Reactants:Na1

O2

Products:Na4

O2

(= Na2O + Na2O)

Na + O2 2Na2O4

solution: Add the coefficient ‘4’ in front of NaTake atomic inventory again:

Reactants:Na4

O2

Products:Na4

O2

4 sodium atoms combine with 1 oxygen molecule to form 2 formula units of sodium oxide. This equation obeys the Law of Conservation of Matter.


BALANCE THE FOLLOWING BALANCE THE FOLLOWING REACTION:REACTION:

HH2(g)2(g) + O + O2(g)2(g) H H22OO(l)(l)

Balancing with polyatomic ionsBalancing with polyatomic ions Sometimes polyatomic ions break apart in a Sometimes polyatomic ions break apart in a

chemical reaction and sometimes they do chemical reaction and sometimes they do notnot e.x. sulfate appears on both sides of the e.x. sulfate appears on both sides of the

reaction so SOreaction so SO44 can be treated like one can be treated like one atom: atom:

MgMg(s)(s) + Cu + CuSOSO44(aq)(aq) Mg MgSOSO44(aq)(aq) + Cu + Cu(s)(s)

e.x. carbonate breaks apart so atoms must e.x. carbonate breaks apart so atoms must be balanced individually:be balanced individually:

CaCaCOCO33(aq)(aq) + HCl + HCl(aq)(aq) CaCl CaCl2(aq)2(aq) + H + H22OO(l)(l) + + COCO22(g)(g)


Balance the following equations:Balance the following equations:

1.1. NaNa22COCO3(s)3(s) + HCl + HCl(aq)(aq) NaCl NaCl(aq)(aq) + CO + CO2(g)2(g) + + HH22OO(l)(l)

2.2. KK22SOSO4(aq)4(aq) + CaCl + CaCl2(aq)2(aq) CaSO CaSO4(s)4(s) + KCl + KCl(l)(l)

1. Combination.1. Combination. Also called synthesisAlso called synthesis

Two or more reactants combine Two or more reactants combine to form one productto form one product

e.x. 2 Nae.x. 2 Na(s)(s) + Cl + Cl2(g)2(g) 2 NaCl 2 NaCl(s)(s)

A + B A + B AB AB

Types of Chemical Reactions.Types of Chemical Reactions.


Which equation represents a synthesis Which equation represents a synthesis reaction?reaction?

2Ca2Ca(s)(s) + O + O2(g)2(g) 2CaO 2CaO(s)(s)

2KClO2KClO3(s) 3(s) 2KCl 2KCl(s) (s) ++ OO2(g)2(g)

2. Decomposition.2. Decomposition.

One reactant decomposes to One reactant decomposes to form two or more products.form two or more products.

2H2H22OO(l)(l) 2H 2H2(g)2(g) + O + O2(g)2(g)

AB AB A + B A + B


Which equation represents a Which equation represents a decomposition reaction?decomposition reaction?

CaCa(s)(s) + O + O2(g)2(g) CaO CaO(s)(s)

2KClO2KClO3(s) 3(s) 2KCl 2KCl(s) (s) ++ OO2(g)2(g)

3. Single Replacement.3. Single Replacement. An atom replaces an ion in a An atom replaces an ion in a

compound.compound.

MgMg(s)(s) + + CuCuSOSO44(aq)(aq) MgMgSOSO44(aq)(aq) + + CuCu(s)(s)

ClCl22(g)(g) + 2 + 2KKII(aq)(aq) II22(s)(s) + 2 + 2KKClCl(aq)(aq)

AA + + BBCC AACC + + BB


Which equation represents a single Which equation represents a single replacement reaction?replacement reaction?

• 2NaI2NaI(s)(s) + Cl + Cl2(g)2(g) 2NaCl 2NaCl(s)(s) + I + I2(s)2(s)

• 2NaI2NaI(aq)(aq) + Pb(NO + Pb(NO33))2(aq)2(aq) 2NaNO 2NaNO3(aq)3(aq) + + PbIPbI2(s)2(s)

4. Double Replacement.4. Double Replacement.

Ions from different compounds Ions from different compounds switch places.switch places.

CaCaCOCO33(s)(s) + 2 + 2HHClCl(aq)(aq) CaCaClCl22(s)(s) + + HH22COCO33(aq)(aq)

AABB + + CCDD AADD + + CCBB


Which equation represents a double Which equation represents a double replacement reaction?replacement reaction?

• 2NaI2NaI(s)(s) + Cl + Cl2(g)2(g) 2NaCl 2NaCl(s)(s) + I + I2(s)2(s)

• 2NaI2NaI(aq)(aq) + Pb(NO + Pb(NO33))2(aq)2(aq) 2NaNO 2NaNO3(aq)3(aq) + + PbIPbI2(s)2(s)

A compound reacts with oxygenA compound reacts with oxygen often produces COoften produces CO22 & H & H22OO e.x. Ce.x. C33HH8(g)8(g) + 5O + 5O2(g)2(g) 3CO 3CO2(g)2(g) + 4H + 4H22OO(g)(g)

NoteNote: a combustion reaction : a combustion reaction cancan also be a also be a decomposition or a combination reactiondecomposition or a combination reaction

5. Combustion reactions.5. Combustion reactions.


Write the balanced equation for the Write the balanced equation for the reaction of CO with Oreaction of CO with O22 to form CO to form CO22 and identify the type of reaction.and identify the type of reaction.

Standard 3e:Standard 3e:The Arithmetic of Equations.The Arithmetic of Equations.

A balanced equation shows the A balanced equation shows the amount of each reactant and amount of each reactant and product needed or produced in product needed or produced in any reaction.any reaction.

Example.Example.

MgMg(s)(s) + 2HCl + 2HCl(aq)(aq) MgCl MgCl2(aq)2(aq) + H + H2(g)2(g)

One atom of magnesium combines One atom of magnesium combines with 2 formula units of HCl to form with 2 formula units of HCl to form one formula unit of magnesium one formula unit of magnesium chloride and one molecule of chloride and one molecule of hydrogen gas.hydrogen gas. Use equation coefficients to solve Use equation coefficients to solve

quantitative problems.quantitative problems.


1.1. How many molecules of oxygen are How many molecules of oxygen are needed to react with 4 atoms of needed to react with 4 atoms of sodium?sodium?

2.2. How many oxygen How many oxygen atomsatoms is that? is that?

3.3. How many formula units of sodium How many formula units of sodium oxide are produced when 4 atoms of oxide are produced when 4 atoms of sodium are used?sodium are used?

4Na(s) + O2(g) 2Na2O(s)

Example.Example. MgMg(s)(s) + 2HCl + 2HCl(aq)(aq) MgCl MgCl2(aq)2(aq) + H + H2(g)2(g) If 1 atom of magnesium is used, 2 If 1 atom of magnesium is used, 2

formula units of HCl are needed to react.formula units of HCl are needed to react. If 6 atoms of magnesium are used, how If 6 atoms of magnesium are used, how

many formula units of HCl are needed?many formula units of HCl are needed?

Fo.U. HCl6 atom Mg

atom Mg

Fo.U. HCl=

2

112

Anatomy of a conversionAnatomy of a conversion

=

T-Chart: multiply everything on top and divide by everything on the bottom

What you know

Conversionfactor

What youget

Given(units)

Units for answer

Units of givenanswer



if 4 molecules of Hif 4 molecules of H22 are created are created

1.1. how many Fo.U. of HCl are needed?how many Fo.U. of HCl are needed?

2.2. How many atoms of Mg are used?How many atoms of Mg are used?

Standard 3b: The MoleStandard 3b: The Mole

Atoms and molecules are so small scientists must use a large number of atoms, molecules or formula units in order to observe chemical reactions. This large number is called: A Mole

The number of particles in one moleThe number of particles in one mole ==

Avogadro’s numberAvogadro’s number

= 6.02 x 10= 6.02 x 102323

= 602,000,000,000,000,000,000,000= 602,000,000,000,000,000,000,000

Particles = atoms,Particles = atoms,

molecules, molecules,

formula units,formula units,

donuts…donuts…

Standard 3c: Avogadro’s NumberStandard 3c: Avogadro’s Number


How many dollars would you have if How many dollars would you have if you had Avogadro’s number of you had Avogadro’s number of dollars?dollars?

Avogadro’s number is convenient Avogadro’s number is convenient because a mole of any chemical is because a mole of any chemical is easily measured in the laboratory.easily measured in the laboratory.

Instead of using 6.02 x 10Instead of using 6.02 x 102323 atoms atoms we use 1 mole of atoms.we use 1 mole of atoms.


1.1. How many moles of How many moles of O2 are needed to are needed to react with 4 moles of sodium?react with 4 moles of sodium?

2.2. How many moles of How many moles of O2 are needed to are needed to react with 2 moles of sodium? react with 2 moles of sodium?

3.3. How many moles of How many moles of Na2O are produced are produced when 2 moles of sodium are used?when 2 moles of sodium are used?

4Na(s) + O2(g) 2Na2O(s)

Moles Moles

particles

mass

volume

6.02x1023 particles

1 mole

22.4

L1

mol

e

Molar mass(g)1 mole

1 mole

6.02x10 23 particles1 mole

Molar mass(g)1

mol

e22

.4L

Standard 3e:stoichiometry

coefficients

1 Mole1 Mole of any atom has a of any atom has a mass (in grams) numerically mass (in grams) numerically equivalent to the mass of a equivalent to the mass of a single atom (in amu). This single atom (in amu). This mass is displayed on the mass is displayed on the periodic table.periodic table.

study question 17 study question 17

What is the mass of one mole of:What is the mass of one mole of: Aluminum?Aluminum? Carbon?Carbon?

Standard 3d: Molar MassStandard 3d: Molar Mass = = the mass of one mole of any substance.the mass of one mole of any substance.

Example: NaExample: Na22OO

Sodium = 23g/moleSodium = 23g/mole

Oxygen = 16g/moleOxygen = 16g/mole

1 mole Na1 mole Na22O:O:

(2x23g/mole) + 16g/mole =(2x23g/mole) + 16g/mole =

The molar mass for NaThe molar mass for Na22O = 62g/moleO = 62g/mole


calculate the molar mass of AlClcalculate the molar mass of AlCl33 (don’t forget units!)(don’t forget units!)

examplesexamples What is the mass of 3 moles of What is the mass of 3 moles of

sodium hydroxide?sodium hydroxide?

g NaOH

3 moles NaOH=

40 g NaOH

1 mole NaOH120

How many moles of carbon dioxide How many moles of carbon dioxide are in a sample weighing 88g?are in a sample weighing 88g?

moles CO2

88g CO2 =1 mole CO2

44g CO2

2

Molar mass!


A person produces just less than 0.5 A person produces just less than 0.5 moles CHmoles CH44 per day. How many per day. How many grams is that?grams is that?

The volume of a MoleThe volume of a Mole

1 mole of any 1 mole of any GASGAS has a has a volume of 22.4L at standard volume of 22.4L at standard temperature and pressuretemperature and pressure

Standard temperature = 0Standard temperature = 0°°CC Standard pressure = 1atmStandard pressure = 1atm


1. What is the volume of 2 moles of gas?2. What is the volume of 0.5 moles of

gas?

(At standard temperature and pressure)

examplesexamples What is the volume of 3 moles of What is the volume of 3 moles of

helium?helium? L He

3 moles He=

22.4 L He

1 mole He67.2

How many moles of nitrogen are How many moles of nitrogen are inside a 224L container?inside a 224L container?

mole N2

224 L=

1 mole N2

22.4 L10


A person produces just less than 11.2L A person produces just less than 11.2L CHCH44 per day. How many moles is per day. How many moles is that (assume STP conditions)?that (assume STP conditions)?

Example.Example.


If 73g hydrochloric acid are used, If 73g hydrochloric acid are used, how many liters of hydrogen gas are how many liters of hydrogen gas are produced?produced?

L H2

73 g HCl

2 moles HCl

1 mole H2

=36.5 g HCl 1 mole H2

22.4L H21 mole HCl22.4


3H3H2(g)2(g) + N + N2(g)2(g) 2NH 2NH3(g)3(g)

If one mole of nitrogen is used how If one mole of nitrogen is used how many moles of hydrogen are needed?many moles of hydrogen are needed?

How many liters of hydrogen are How many liters of hydrogen are needed to produce 17g of NHneeded to produce 17g of NH3(g)3(g)? ?

examplesexamples How many molecules are contained How many molecules are contained

in 2 moles of COin 2 moles of CO22??

molecules

CO2

2 moles CO2=

6 x 1023 molecules

1 mole CO2

12 x 1023

How many How many atomsatoms are contained in 2 are contained in 2 moles of COmoles of CO22??

= 1.2 x 1024

atoms2 mol CO2 =6 x 1023 molcs

1 mol CO2

36 x 10233 atoms

1 molc CO2 = 3.6 x 1024


A cow produces about 1500L CHA cow produces about 1500L CH44 per per day. How many molecules is that?day. How many molecules is that?

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Stoichiometry. Chapter 9, 10, & 11