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Intro to Chemical Reactions
Chapter 6
How do you know if a chemical
reaction occurred?
We look for visual signs OR a chemical change
-If something bubbles, changes color, forms a solid (precipitate) or combusts the system has underwent a chemical change a new product exists.
Classifying reactions
In every reaction we have reactions and products
Reactants- are the chemicals present in the system
Products- are chemicals formed by the system
Types of Chemical reactions
Synthesis reactions-- 2 or more chemicals combine to form a
more complex product- A + B AB
- Examples:- The formation of potassium chloride from
potassium and chlorine gas:- 2K (s) + Cl2 (g) 2KCl
Reaction Types Cont…
Decomposition:A compound is broken down into smaller chemical species
AB A + B
Examples:
2KCl 2 K (s) + Cl2 (g)
2H2O 2H2 + O2
Reaction Types Cont…
Single Replacement (aka substitution reaction)-
One element being replaced by another element to form a compound.
A + BC AC + B
Examples:
3 Ag NO3 (aq) + Al (s) Al (NO3)3 (aq) + 3 Ag (s)
Zn + 2HCl ZnCl2 + H2
Reaction Types Cont…
Double Replacement-2 elements are being replaced to form 2 new compounds
AB + CD AD + CB
Examples:
AgNO3 + NaCl AgCl + NaNO3
SiO2 + 4HF SiF4 + 2H2O
Reaction Types Cont…
Combustion-A hydrocarbon usually reacts with oxygen to form carbon dioxide and water
Hydrocarbon + Oxygen (O2) CO2 + H2O
Examples:CH4 + 2O2 CO2 + H2O
2C2H6 + 7O2 4 CO2 + 6H2O
Practice problems:
When solid ammonium nitrite is heated, it produces nitrogen gas and water vapor
NH4NO2 N2 + 2H2O
Practice Problems
Gaseous nitrogen monoxide decomposes to produce di nitrogen monoxide gas and nitrogen dioxide gas
3NO N2O + NO2
Practice Problems
Solid mercury oxide decomposes to produce liquid mercury metal and gaseous oxygen
2HgO 2Hg + O2
Practice Problems
Solid carbon reacts with gaseous oxygen to form gaseous carbon dioxide
C + O2 CO2
Practice Problems
Solid zinc is added to an aqueous solution containing dissolved hydrogen chloride to produce gaseous hydrogen that bubbles out of the solution and zinc chloride that remains dissolved in the water
Zn + 2HCl ZnCl2 + H2