Chemistry Fall 2013. Chemical Reactions A chemical reaction is a process in which one or more...
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Transcript of Chemistry Fall 2013. Chemical Reactions A chemical reaction is a process in which one or more...
![Page 1: Chemistry Fall 2013. Chemical Reactions A chemical reaction is a process in which one or more substances are converted into new substances with different.](https://reader036.fdocuments.net/reader036/viewer/2022082709/56649cf95503460f949ca5b3/html5/thumbnails/1.jpg)
Chemical Reactions & Equations
Chemistry Fall 2013
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Chemical Reactions A chemical reaction is a process in which one
or more substances are converted into new substances with different physical and chemical properties.
All chemical reactions involve 2 types of substances:Reactants- substances present before the
chemical reactionProducts- the substance or substances
produced by the chemical reaction
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Chemical Reactions cont…Some substances do not under go chemical
reactions because they have a full set of valence electrons
Chemical reactions allow substances to obtain a complete set of valence electrons.
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Chemical Equations Chemical reactions are represented by
sentences known as chemical equations. Chemical equations describe what happens in
a chemical reaction.
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Chemical Equations cont… Word equations
Simplest type of chemical equationEx: calcium + oxygen → calcium oxide
Arrow indicates the direction of the reaction
Formula equationsEx: Ca + O2 → CaO Be sure to use the correct symbols and
formulas for reactants and products.
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Balancing Chemical Equations Remember the law of conservation of mass?
Mass can be neither created or destroyed Mass is neither created or destroyed during a
chemical reactions Mass of total products must equal mass of
the total reactants For mass to remain constant before and after
a chemical reaction, the number of atoms of each element must be the same before and after a chemical reaction.
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Balancing Chemical Equations cont…When balancing a chemical equation DO NOT
ever change the subscripts, as this changes the compound being used to produce the reaction or the product of the reaction.
To balance a chemical equation you change the coefficients (whole numbers written before the formulas) for the reactants and products.
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Balancing Chemical Equations cont…Steps to balance a chemical equation
1. Write the formula equation with correct symbols & formulas.
2. Count the number of atoms of each element on each side of the arrow.
3. Balance atoms using coefficients.4. Check your work by counting atoms of each
element.
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Balancing Chemical Equations cont…Ex: Ca + O2 → CaO
Ex: Na + Cl2 → NaCl
Ex: CH4 + O2 → CO2 + H2O
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Classifying Chemical Reactions Some reactions combine elements to form
compoundsSome reactions break down compounds into
elementsIn some reactions, one element replaces
another in a compound. There are 4 general types of chemical
reactions:Direct combinationDecompositionSingle-replacementDouble-replacement
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Classifying Chemical Reactions Direct combination reactions
Two or more reactants come together to form a single product
Also known as synthesis reactions A + B → AB This is the only type of reaction in which there is a single
product 2 or more simple reactants form a single, more complex product
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Classifying Chemical Reactions Decomposition Reactions
a single compound is broken down into two or more smaller compounds or elements
Reverse of a direct combination reactions There is only one reactant AB → A + B
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Classifying Chemical Reactions Single- Replacement Reactions
An uncombined element displaces an element that is part of a compound
Reactants are always one element and one compound
A + BX → AX + B BX & AX are generally ionic compounds
Not all elements can replace other elements Depends on chemical reactivity Usually metals replace nonmetals or hydrogen and nonmetals
replace metals
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Classifying Chemical Reactions Double-replacement Reactions
Atoms or ions from two different compounds replace each other
Two compounds as reactants and two compounds as products
AX + BY → AY + BX