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Questions and Answers
According to the law of conservation of mass, mass cannot be created or destroyed in a chemical ______.
According to the law of conservation of mass, mass cannot be created or destroyed in a chemical ______.
reaction
An equation that gives the same number of each type of atom on both sides is called a ______ equation.
An equation that gives the same number of each type of atom on both sides is called a ______ equation.
balanced
The numbers placed in front of the formulas in a chemical equation are known as ______.
The numbers placed in front of the formulas in a chemical equation are known as ______.
coefficients
When no coefficient is written, it is assumed to be ______.
When no coefficient is written, it is assumed to be ______.
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It is easier to balance elements in a chemical equation that appear only ______.
It is easier to balance elements in a chemical equation that appear only ______.
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Single replacement reactions involve one element taking the place of another in a ___.
Single replacement reactions involve one element taking the place of another in a ___.
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The general form for a double replacement reaction is ___ + DZ → DX + AZ.
The general form for a double replacement reaction is ___ + DZ → DX + AZ.
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In combustion reactions, a substance combines with ___ and burns, releasing energy.
In combustion reactions, a substance combines with ___ and burns, releasing energy.
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The reaction of 2K + ZnCl2 → 2KCl + Zn is an example of a ___ reaction.
The reaction of 2K + ZnCl2 → 2KCl + Zn is an example of a ___ reaction.
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Hydrocarbon combustion typically follows the form CXHY + O2 → CO2 + H2O, where X and Y represent the number of ___ and hydrogen atoms.
Hydrocarbon combustion typically follows the form CXHY + O2 → CO2 + H2O, where X and Y represent the number of ___ and hydrogen atoms.
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Study Notes
Chemical Reactions
- A chemical reaction is the rearrangement of atoms in one or more substances to form one or more new substances.
- This is represented by a chemical equation.
Reactants and Products
- Reactants are the substances that enter into a chemical reaction.
- Products are the substances that are formed as a result of the reaction.
- Reactions are indicated by the arrow "→" and reactants are listed on the left side of the arrow, while products are listed on the right side of the arrow.
Other Signs of Chemical Reactions
- Gas production
- Light production
- Solid precipitate formation (when two solutions are mixed)
- Temperature change (exothermic or endothermic)
- Color change (permanent)
Diatomic Molecules
- Some elements only exist in nature in diatomic form (two atoms bonded together).
- The diatomic elements are hydrogen (H₂), nitrogen (N₂), oxygen (O₂), fluorine (F₂), chlorine (Cl₂), bromine (Br₂), and iodine (I₂).
- They are always written with a subscript of 2 in a chemical formula, as they cannot exist on their own.
Writing Chemical Equations
- Chemical equations use formulas to describe chemical reactions.
- Formulas show atoms and molecules involved in a reaction.
- Symbols and formulas are needed to represent the reaction accurately; hence the importance of knowing nomenclature rules.
Balancing Chemical Equations
- The law of conservation of mass states that mass cannot be created or destroyed in a chemical reaction.
- The number of atoms of each element must be the same on both sides of the equation.
- Coefficients are used to balance the number of atoms of each element on both sides of the equation.
Types of Chemical Reactions
- Synthesis (two or more substances combine to form a new substance)
- Decomposition (a substance breaks down into two or more substances)
- Single replacement (one element replaces another element in a compound)
- Double replacement (the positive ions (cations) and the negative ions (anions) in two compounds swap places).
- Combustion (a substance reacts rapidly with oxygen, often producing heat and light).
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Description
Explore the world of chemical reactions through this quiz. Learn about reactants and products, the signs of chemical reactions, and diatomic molecules. Test your knowledge on how substances transform and the principles underlying chemical equations.
