Wednesday Bellwork

• How many atoms are in each of the following compounds?– H2SO4

– Ca(NO3)2

– (NH4)3PO4

– C6H12O6

– 2 H2O

– 10 CO2

7 atoms!

9 atoms!

20 atoms!

24 atoms!

6 atoms!

30 atoms!

CHEMICAL REACTIONS

8.1 Chemical reaction-

• the changing of substances by the breaking of bonds in reactants and the formation of bonds in products.

Evidence of a chemical reaction:

1. Release of a gas

Zinc is added to hydrochloric acid producing hydrogen gas and solid zinc chloride.

2. Color changes

two liquids are mixed

solid and a liquid mixed

3. Formation of a precipitate– a precipitate is a solid product formed by the

reaction of two aqueous solutions.

– It is abbreviated ppt.

Aqueous sodium iodide and aqueous lead (II) nitrate produce solid lead (II) iodide and aqueous sodium nitrate.

4. Changes in heat and light– all reactions either absorb or release energy

Sodium peroxide (yellow powder) and zinc powder (gray powder in the bowl) are combined

Water is then squirted in & the mixture ignites

Demo Time!

• Rusty, Crusty Steel Wool!

Writing Chemical Equations:

reactants productsyield

Na + Cl2 NaCl

EXAMPLE:

Possible symbols in chemical equations:

• + plus yields• (s) solid• (l) liquid• (g) gas• (aq) aqueous equilibrium• N.R. no reaction heat is added• catalyst

(light or heat) & catalysts are written above the yield sign

Examples: To what is the arrow pointing?

H2O2 (aq) H2O (l) + O2 (g)MnO2

CaCO3 CaO (s) + CO2 (g)

H2 (g) + O2 (g) H2O (g)

Writing and Balancing Chemical Equations

Example:

Write the equation for the formation of sodium hydroxide and hydrogen, from the reaction of sodium with water.

Write the equation for the formation of sodium hydroxide and hydrogen, from the reaction of sodium with water.

1.Write the formulas of all reactants to the left of the arrow and all products to the right of the arrow.

Sodium + water

Translate the equation and be sure the formulas are correct.

Na + H2O NaOH + H2

sodium hydroxide + hydrogen

Write the equation for the formation of sodium hydroxide and hydrogen, from the reaction of sodium with water.

2.Once the formulas are correctly written, DO NOT change them. Use coefficients (numbers in front of the formulas), to balance the equation. DO NOT CHANGE THE SUBSCRIPTS!

_____Na + _____H2O ____NaOH + _____H2

3.Begin balancing with an element that occurs only once on each side of the arrow.

Ex: Na

_____Na + _____H2O ____NaOH + _____H2

Na

H

O

Na

H

O

222

4

2

2

2

4

2

When you are finished, you should have equal numbers of each element on either side of the equation

4.To determine the number of atoms of a given element in one term of the equation, multiply the coefficient by the subscript of the element.

Ex: In the previous equation (below), how many hydrogen atoms are there?

4

____Na + _____H2O ____NaOH + _____H22 2 2

• Balance elements one at a time.

• Balance polyatomic ions that appear on both sides of the equation as single units. (Ex: Count sulfate ions, not sulfur and oxygen separately)

• Balance H and O last. Save the one that is in the most places for last…

• Use Pencil!

(NH4)2SO4 (aq) + BaCl2 (aq) BaSO4 (s) + NH4Cl (aq)

Practice:• Balance the equation for the formation of

magnesium nitride from its elements.

____Mg + ____N2

Mg2+ N3-

Mg3N2

3 ____Mg3N2

Balance the reaction of sodium metal with chlorine gas to form sodium chloride.

____Na + ____Cl2

NaCl

Cl-Na+

22 ____NaCl

Coefficients are always whole numbers:

• Sometimes though, fractions seem necessary.

Ex: NH3 + O2 NO2 + H2O

• H can be balanced by placing a 2 in front of NH3 and a 3 in front of H2O. Then put a 2 in front of NO2 for nitrogen to balance.

_____NH3 + _____O2 ____NO2 + ____H2O2 32

• Now all that is left to balance is the oxygen. There are 2 O on the reactant side and 7 on the product side. Our only source of oxygen is the O2. Any whole number we place in front of the O2 will result in an even number of atoms. The only way to balance the equation is to use a coefficient of 7/2.

_____NH3 + _____O2 ____NO2 + ____H2O2 327/2

• On a molecular level this makes no sense. You cannot have ½ of an O2 molecule. So…to get rid of the fraction, multiply all the coefficients by 2 (the denominator).

_____NH3 + _____O2 ____NO2 + ____H2O2 327/2

____NH3 + _____O2 ____NO2 + ____H2O2 327/2( )2

=

_____NH3 + _____O2 ____NO2 + ____H2O4 647

____H2 + ____O2 ____H2O

___NH3 + ____O2 ____NO2 + ____H2O

___Ca + ___H2O ___Ca(OH)2 + ___H2

__NH4Cl +__Ca(OH)2 __NH3 + __H2O+__CaCl2

___ZnO + ___HCl ___ZnCl2 + ___H2O

____K + _____F2 _____KF

____C2H4 + ____O2 ____CO2 + ____H2O

Thursday Bellwork

• Balance the following equations.

• ___Zn + ___HCl ___ZnCl2 + ___H2

•  __Al2(SO4)3 + __Ca(OH)2 __Al(OH)3 + __CaSO4

•   __K + __H2O __KOH + __H2

•   __CH4 + __O2 __CO2 + __H2O

Synthesis reaction (combination reaction)-

• the combination of two or more substances to form a compound

Elem. or cmpd. + elem. or cmpd cmpd.

General form A + B AB

• The product in a reaction will have different properties from either of the reactants that formed it.

EXAMPLES:

_____Na + _____Cl2

_____Fe + _____O2

_____Al + _____Cl2

_____H2O + _____CO2

____NaCl

____Fe2O3

H2CO3

____AlCl3

2

232

2

4

3 22

Decomposition Reaction:

• is the breakdown of one substance into two or more other substances

• compound two or more elements

• AB A + B

____H2CO3 ____H2O + ____CO2

_____KCl

_____HCl

____K + ____Cl2

____H + ____Cl22

2 2

2

Friday Bellwork

• Predict the products of the following reactions and balance the equation.– Ca + N2

– Cl2 + Fe (iron III)

– MgO + CO2

– Mg3N2

– Li3N

– H2CO3

Single Replacement Reaction:

• One element replaces another element in a compound.

element + compound element + compound

A + BC AC + B

___Zn + ___HCl

___Cl2 + ___KI

___ZnCl2 + ___H2

___KCl + ___I2

2

22

To determine if a single replacement reaction will take place you must compare the activities of the elements involved.

• For metals, use the Activity Series (pg. 217). A metal will replace any metal below it on the activity series.

Activity Series of Metals and HalogensMetals Halogens

Deceasing activityLithium FluorinePotassium ChlorineCalcium BromineSodium IodineMagnesiumAluminumZincChromiumIronNickelTinLeadHYDROGENCopperMercurySilverPlatinumGold

Will Na replace Cr in a single replacement reaction?

Yes!

Practice:___I2 + ___NaCl

___AgNO3 + ___Mg

___KBr + ___F2

___Mg(NO3)2 + ____Cu

N.R.

___Mg(NO3)2 + ___Ag

___KF + ___Br2

N.R.

2 2

2 2 Activity Series of Metals

LithiumPotassiumBariumCalciumSodiumMagnesiumAluminumZincIronCadmiumNickelTinLeadHydrogen (a nonmetal)CopperMercurySilverGoldPlatinum

Metals from Li to Na will replace H from water and acids; metals from Mg to Pb will replace H

from acids only.

Decreasing A

ctivity

Double Replacement Reaction:

• Two elements replace each other in compounds.

AB + CD AD + CB

MgCO3 + 2HCl MgCl2 + H2CO3

AgNO3 + NaCl AgCl + NaNO3

In order for double replacement reaction to take place, one of the products must be an insoluble solid (ppt), a gas, or a molecular compound (like H2O). Solubility rules on pg 227 list common insoluble substances.

Negative Ion Plus Positive Ion Form a Compound Which is:

Any negative ion + Alkali metal ions(Li+, Na+, K+, Rb+, Cs+)

Soluble

Any negative ion + Ammonium ion Soluble

Nitrate + Any positive ion Soluble

Acetate + Any positive ionAg+

SolubleNot soluble

Chloride, Bromide, or Iodide

+ Ag+, Pb2+, Hg22+, Cu+

Any other positive ion

Not solubleSoluble

Sulfate + Ca2+, Sr2+, Ba2+, Ra2+, Ag+, Pb2+

Any other positive ionNot solubleSoluble

Sulfide + Alkali ions or Ammonium, Be, Mg, Ca, Sr, Ba, Ra,Any other positive ion

SolubleSolubleNot soluble

Hydroxide + Alkali ions or AmmoniumAny other positive ion

SolubleNot soluble

Phosphate, Carbonate, or Sulfite

+ Alkali ions or AmmoniumAny other positive ion

SolubleNot soluble

The Solubility Song!To the tune of “ My Favorite Things” from “The Sound of Music”

Nitrates and Group One and Ammonium,These are all soluble, a rule of thumb.Then you have chlorides, they’re soluble fun,All except Silver, Lead, Mercury I.Then you have sulfates, except for these three:Barium, Calcium and Lead, you see.Worry not only few left to go still.We will do fine on this test. Yes, we will!Then you have the---InsolublesHydroxide,Sulfide and Carbonate and Phosphate,And all of these can be dried!

CompoundPrecipitate Formed?

• BaSO4 _______

• Pb(NO3)2 _______

• Ag2S _______

• PbCl2 _______

• NH4Cl _______

• Cr PO4 _______

Yes

YesNo

Yes

Yes

No

__Na2SO4 + __Ba(NO3)2

__NaOH + __Fe(NO3)3 __NaNO3 + __Fe(OH)3

__NaNO3 + __BaSO4 2

3 3

Na+ NO3-

NaNO3

Ba2+ SO42-

BaSO4

Na+ NO3-

NaNO3

Fe3+ OH-

Fe(OH)3

Bellwork

• Write the products of the following reactions. Balance the equation when you are done.

•   Ni(s) + MgSO4(aq)

•   Br2(l) + CaCl2(aq)

•   zinc + copper(II) nitrate

• An exothermic reaction in which a substance combines with oxygen forming products in which all elements are combined with oxygen. (Burning) Energy is usually released in the form of heat and light.

General form for combustion of a hydrocarbon:

CxHy + O2 CO2 + H2O

Examples

____C3H8 + ____O2

____C6H12O6 + ____O2

____Mg + ____O2

____CO2 + ____H2O

____CO2 + ____H2O

____MgO

3 45

6 66

22

Tuesday Bellwork

• Write the type of reaction on the left and complete and balance the equation on the right.

• Type Equation

• ____Li + O2

• ____Cl2 + MgF2

• ____C5H12 + O2

• ____MgCO3

• ____AgNO3 + NaCl

Monday Bellwork

• Convert the following word equations into formulas, complete the equation, and balance.– Copper (II) sulfide is added to barium hydroxide

– Ethanol (C2H5OH) is burned in oxygen

– Magnesium metal is added to nitrogen gas

– Magnesium carbonate is heated

Quiz InformationNegative Ion Plus Positive Ion Form a Compound

Which is:

Any negative ion + Alkali metal ions (Li+, Na+, K+, Rb+, Cs+) Soluble

Any negative ion + Ammonium ion Soluble

Nitrate + Any positive ion Soluble

Acetate + Any positive ionAg+

SolubleNot soluble

Chloride, Bromide, or Iodide

+ Ag+, Pb2+, Hg22+, Cu+

Any other positive ion

Not solubleSoluble

Sulfate + Ca2+, Sr2+, Ba2+, Ra2+, Ag+, Pb2+

Any other positive ionNot solubleSoluble

Sulfide + Alkali ions or Ammonium, Be, Mg, Ca, Sr, Ba, Ra,Any other positive ion

SolubleSolubleNot soluble

Hydroxide + Alkali ions or AmmoniumAny other positive ion

SolubleNot soluble

Phosphate, Carbonate, or Sulfite

+ Alkali ions or AmmoniumAny other positive ion

SolubleNot soluble

Quiz InformationMetals Halogens

Deceasing activityLithium FluorinePotassium ChlorineCalcium BromineSodium IodineMagnesiumAluminumZincChromiumIronNickelTinLeadHYDROGENCopperMercurySilverPlatinumGold