wednesday bellwork how many atoms are in each of the following compounds? –h 2 so 4 –ca(no 3 ) 2...
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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