Transcript + H 2 SO 4(aq) - Rothschild Science

Warm Up: Determine the name and molar mass of the
following compounds.
MnO2
H2SO4
1
How did you do?
MnO2- 86.94 g/mol, Manganese (IV) oxide
H2SO4 98.09 g/mol, Sulfuric acid
Be sure you go back and review the basics…
2
BALANCING EQUATIONS &
CHEMICAL REACTIONS
Evidence of Chemical Change





Changes in Energy (E)
Release of E as heat
Release of E as light
Production of sound
Reduction or increase of
temperature
Absorption or release of
electrical Energy




Formation of new
substances
Formation of a gas
Formation of a
precipitate
Change in color
Change in odor
Conservation of Mass
Law of Conservation of Mass
 In any physical or chemical reaction, mass
is neither created nor destroyed; it is
conserved!
Reactants
Products
Same number of atoms on both
sides of the equation!
Balancing Equations
In every balanced equation
each side of the equation
has the same number of atoms
of each element
Parts of a Reaction
 Subscripts – tells how many atoms of each
element you have NH3 (one nitrogen, three
hydrogen)- DON’T mess with these!!
 Coefficients – small whole number that appears
in front of a chemical formula in an equation –
you get to “mess” with these. 2NH3 (Two
molecules of ammonia or two moles of ammonia)
  the arrow means yields or reacts to produce
REACTANTS
PRODUCTS
You have to get the same number of elements
on each side of the reaction
Balancing Rules
1.
2.
3.
4.
Never touch subscripts when balancing
equations, you will change the substance
Include all sources of the element
CH3CHOOH + NaOH
Polyatomic ions that appear intact on both
sides of the equation, can be balanced as a
group (PO4)
Coefficients in your balanced equation contain
the lowest possible ratio.
Balancing!
Aluminum + Oxygen  Aluminum Oxide
Al + O2  Al2O3
Until you get good at this, it is helpful
to write the number of atoms of each element on
both sides of the equation. It helps you to keep
track of the atoms.
Balancing!
Ethene + Oxygen  Carbon Dioxide + water
C2H4 + O2  CO2 + H2O
Balancing!
Hydrogen gas + nitrogen gas  ammonia
Remember your diatomic molecules!!!
H2 + N2  NH3
Try this one!
NaNO3 + CrCl3  NaCl + Cr(NO3)3
Important stuff!
Four abbreviations are
used to indicate
physical states of
chemicals: shown as
subscripts in the chemical
equation
(s) = solid
(l) = liquid
(g) = gas
(aq)= aqueous solution
(dissolved in water)
Symbols over the arrow
indicate the conditions of
the reaction
Heat
Pressure
Temperature
Catalyst
Reversible reaction
Warm Up-
Use percent composition to determine the
amount of chlorine produced in the
decompostion of 402.3 g of calcium chloride.
Questions on the Formula Review?
Balance this equation…
NaNO3 + CrCl3  NaCl + Cr(NO3)3
How would you “write” it?
Let’s look at the front side of the
Balancing Equations WS
How did you do?
REACTIONS
Combination Reaction
or Synthesis Reaction
 Two or more simple substances react to
form a more complicated one
A + B  AB
Fe + S  FeS
Combination Reactions
We can predict the products of ionic compounds by
thinking about the charge!
Al (s) +
O2 (g) 
Cu (s) +
S(s)

Are there 2 possible products to this reactions
How would we “say” these equations?
Decomposition Reaction
 A decomposition reaction is the opposite
of a composition reaction - a complex
molecule breaks down to make simpler
ones.
AB  A + B
2 H2O  2 H2 + O2
Decomposition Reactions
Harder to predict the products…always remember
your diatomics.
Water is often a product!
HgO(s) 
NH4NO3
Decomposition Reactions
HgO(s)
2HgO(s)


2Hg(l)
+
O2 (g)
NH4NO3
NH4NO3


N2O
+
2H2O
The only way to really know is to do the
reaction!!
Single Replacement
 This is when one element trades places with
another element in a compound.
A + BC  AC + B
Mg + 2H2O  Mg(OH)2 + H2
Single Replacement Reactions
Easy to predict the products. Look at the ions…
remember that a cation has to bond to an anion!!
Don’t forget about diatomics!
Zn(s) +
H2SO4(aq) 
Na(s) +
H2O 
OOPS! Did we balance them?
Single Replacement Reactions

 ZnSO4(aq)
Zn(s) +
Zn(s) +
H2SO4(aq)
H2SO4(aq)
Na(s) +
Na(s) +
2Na(s)+
H2O 
H+OH-(l) 
2H+OH-(l)  2NaOH
+ H2(g)
+ H2(g)
Single Replacement Reactions
Reactivity of a metal makes a difference!
If a metal is more reactive than the metal it is
displacing a rxn will occur. If the metal is
less reactive than the metal it is
displacing, a rxn will not occur.
Metal Reactivity
Increases down a group
Decreases across a period
Brainiacs-- Metal Reactivity
Reactivity in Single Displacement
+ KMnO4  CsMnO4
Will this occur??
Cs
Na
+
KMnO4  NaMnO4 + K
Will this occur?
Double Replacement Reaction
 This is when the anions and cations of two
different molecules switch places, forming
two entirely different compounds
AB + CD  AD + CB
Pb(NO3)2 + 2KI  PbI2 + 2KNO3
Double Replacement Reactions
Generally take place between two ionic compounds in
aqueous solution
Generally 3 things happen:
1.
A precipitate (solid) occurs
Pb(NO3)2 + 2KI  PbI2 + 2KNO3
Double Replacement Reactions
2.
One product is a gas that bubbles out of
the mixture
2NaCN(aq) + H2SO4  2HCN(g) + Na2 SO4(aq)
Double Replacement Reactions
3.
One product is a molecule while the
other products are ions
Ca(OH)2(aq) + 2HCl(aq)  Ca+2 + Cl- + 2 H2O(l)
Warm UpBalance the following equations:
C3H6 +
O2 
CO2 + H2O
C7H14 +
O2 
CO2 + H2O
Show Period 2
Brainiacs-- Metal Reactivity
Combustion Reactions
 A combustion reaction is when oxygen
combines with another compound or
element producing energy.
 When hydrocarbons (C?H?) combust,
water, carbon dioxide and energy are
produced.
C10H8 + 12 O2  10 CO2 + 4 H2O + Energy
Combustion of Naphthalene
Combustion Reactions
Combustion of propane:
C3H8 +
O2

Combustion of methane:
CH4 +
O2

Combustion of butene (this one is tricky!)
C4H6 +
O2

Teacher Demo Extraordinaire!
What is a flame video- Science Friday
http://www.sciencefriday.com/video/06/08/2012/
what-is-a-flame.html
Recap: 5 Types of Reactions
1.
2.
3.
4.
5.
Combination
Decomposition
Single Replacement
Double Replacement
Combustion
Let’s talk about what you should
take next year…
Predict the products, balance and classify
the following reactions.
Li + MgCl2 
C6H12 + O2 
Ca(NO3)2 + NaOH 
Work on the predicting products
WS
Finish it as homework
The analysis articles are on the website…
will be due on test day. You can turn it in
anytime between now and then.
Warm Up
Do the first 2 problems on the Balancing Word
Equations WS…..do both front and back!!
What do the equations mean?
The coefficients indicate the number of moles of
the reactants necessary… to form a certain
mole of the product.
Mole to Mole Ratio
3K + AlCl3  Al + 3KCl
Word Equation WS
Don’t worry too much about the evidence!
Look for changes in state.
Types of Reaction Lab
1.
Divide your paper in half. Label each box, write the
type of reaction, the reactants and predict the
products for the following reactions (form
hypothesis).
a. Synthesis: Mg + O2
b. Decomposistion CaCO3
c. Single Replacement Zn + HCl
d. Double Replacement PbNO3 + KI
In each box…
1. Collect whatever data is asked for on the lab
instruction sheet.
2. Draw a picture of the set up.
3. Write observations… evidence that a
chemical change occurred.
4. Is the reaction endothermic or exothermic?
Warm Up QuizPredict the products, balance and classify the following reactions.
1. K + AlCl3 
2. Ca3(PO4)2 + Ba(OH)2 
3. O2 + C4H10 
Classify the type of reaction for each
of the above equations.
Let’s Grade it!
1. K + AlCl3 
2. Ca3(PO4)2 + Ba(OH)2 
3. O2 + C4H10 
Debrief Types of Rxns Lab
Types of Reaction Lab
Synthesis: Mg + O2 
Did the mass of the system change after the reaction
took place?
Did you detect the presence of ammonia gas?
Endothermic or exothermic?
Types of Reaction Lab
Decomposition CaCO3 
What evidence indicates a chemical reaction.
How do you know that carbon dioxide was formed?
Endothermic or exothermic?
Types of Reaction Lab
Single Replacement
Zn + HCl 
What evidence did you see?
What was in the little tube– how do you know?
Endothermic or exothermic?
Types of Reaction Lab
Double Replacement
PbNO3 + KI 
What evidence did you see?
Endothermic or exothermic?
Last thing…
Revisit your hypothesis… rewrite the correct
balanced equation.
Let’s look at the predicting WS
Questions on the Word Equations
WS?
Will a reaction occur???
Let’s look at the Activity Series and see.