chemical equations and formulas test review subscripts give the correct ratio of _________? atoms a...
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Chemical Equations and Formulas Test Review
Subscripts give the correct ratio of _________?
ATOMS A coefficient tells us the number of ________________ ?
MOLECULES
Chemical Equations and Formulas Test Review
2C10H22 + O2 → CO2 + 22H2O is an example of___?
A CHEMICAL EQUATIONThe left side of the equation shows the______ and
the right side shows the ______. REACTANTSPRODUCTSThe arrow in the middle of the equation separating
the reactants and products is called the _________.
YIELD SIGN
Chemical Equations and Formulas Test Review
Why must chemical equations be balanced?
BECAUSE THE LAW OF CONSERVATION OF MASS STATES THAT MATTER CAN NOT BE DESTROYED OR CREATED, ATOMS IN A REACTION ARE ONLY REARANGED TO FORM NEW SUBSTANCES
What is the first step to balance an equation?COUNT THE NUMBER OF ATOMS FOR EACH
ELEMENT ON BOTH SIDES OF THE EQUATION
Chemical Equations and Formulas Test ReviewWhat is done to fix an unbalanced equation?YOU CHANGE COEFFICIENTS AS NEEDED
Can you change the subscript to balance an equation? Give an explanation why you can or can’t change subscripts.
YOU CAN NEVER CHANGE A SUBSCRIPT TO BALANCE AN EQUATION.
BECAUSE IF YOU CHANGE THE SUBSCRIPT, YOU ARE CHANGING THE SUBSTANCE. FOR EXAMPLE O2 IS ATMOSPHERIC OXYGEN AND O3 IS OZONE, 2 COMPLETELY DIFFERENT SUBSTANCES
Chemical Equations and Formulas Test Review
Fe + 4H2O →Fe3O4 + 4H2 Count the Atoms for the equation.
Fe= 1 Fe= 3H= 8 H = 8O= 4 O= 4
The equation is unbalanced, what changes do you make to balance this equation?
ADD A 3 TO THE IRON (Fe) REACTANT SIDE 3Fe + 4H2O →Fe3O4 + 4H2
Chemical Equations and Formulas Test Review2NCl3 → N2 + Cl2 Is this a balanced equation? Balance if needed.
NO, YOU NEED TO ADD A COEFFICENT OF 3 IN FRONT OF CHLORINE. 2NCl3 → N2 + 3Cl2
H2O +SO3 → H2SO4 Is this a balanced equation? Balance if needed.
YES THIS IS A BALNCED EQUATION
H3BO3 + K → B + KOH Is this a balanced equation? Balance if needed
NO, YOU NEED TO ADD A COEFFICENT OF 3 IN FRONT OF POTTASIUM ON BOTH SIDES OF THE EQUATION H3BO3 + 3K → B + 3KOH
Chemical Equations and Formulas Test Review
C
What is the chemical formula for the model ?
CH4
H
H
H
H
Chemical Equations and Formulas Test Review
1 2 3 Which model represents the formula NH2 ?
MODEL NUMBER 3
Chemical Equations and Formulas Test Review
What is the difference between a compound and molecule?
A molecule is formed when two or more atoms join together chemically. A compound is a molecule that contains at least two different elements. Elements are pure.
Molecule Example--H2
Compound Example -- CaCo3 (also a molecule)
CH4 + O2 CO2 + H2O Balance this equation
CH4 + 2O2 CO2 + 2H2O
Chemical Equations and Formulas Test Review
How many elements are in the compound 2H3PO4
THREE, HYDROGEN, PHOSPHORUS, AND OXYGENHow many molecules are present in the compound
above?TWO MOLECULES OF H3PO4
C4H10 + O2 4CO2 + 5H2O
How many molecules are produced from burning propane?
9, 4CO2 + 5H2O
Chemical Equations and Formulas Test Review
+ +
+ +
+
1
2
3 +
Which model best represents the law of conservation of mass?
MODEL 3 – 6 ATOMS IN REACTION, 6 IN PRODUCT
Balance the following equationsFe + Cl2 FeCl3
2 Fe + 3 Cl2 2 FeCl3
N2 + H2 NH3
N2 + 3 H2 2 NH3
NaCl + F2 NaF + Cl2
2 NaCl + F2 2 NaF + Cl2
What will be different about a chemical change verses a physical change in looking at the chemical formula?
In a physical change, the substance’s chemical formula does not change.
Ex: Boiling water is still H2O but in vapor gas form.
In a chemical change, the atoms and elements have rearranged to form new substances with new and different properties.
Ex: Sodium, a reactive metal, reacts with Chlorine gas to yield NaCl, table salt.