Terms in this set (31)
To know for certain that a chemical reaction has taken place must have evidence that what?
Evidence that one or more substances have undergone a change in identity.
Absolute proof that change of identity has occurred can be provided only by what?
Chemical analysis of the products
Evidence that the chemical reaction has occurred:
Release of heat or light, production of gas, formation of a precipitate and color change.
What does it mean if a reaction involves only the release of heat or light and not both?
It means that the reaction is not necessarily a sign of chemical change because many physical changes also involved either heat or light.
A solid that is produced as a result of a chemical reaction in solution and that separates from the solution.
A properly written chemical equation can summarize any what?
Requirements for writing and reading chemical equations
The equation must represent known facts, equation must contain the correct formulas for the reactants and products, the law of conservation of mass must be satisfied.
In a chemical equation all what must be identified through through what means?
All reactants and products must be identified. through chemical analysis in the laboratory or from sources that give the results of experiments.
Knowledge of what will enable you to supply formulas for reactants and products if they are not available?
Knowledge of the common oxidation states of elements and of methods of writing formulas
What do you do to balance the numbers of atoms ?
Add coefficients where necessary
Small whole number that appears in front of a formula in a chemical equation.
Placing a coefficient in front a very formula specifies the relative number of what?
Of moles of the substance
Equation in which the reactants and products in a chemical reaction are represented by words.
A word equation has only what meaning?
Qualitative does not tell the whole story in terms of quantities.
Represents reactants and products of a chemical reaction by their symbols or formulas
A formula equation meets two of the three requirements for a correct chemical equation
Represent facts and shows the correct symbols and formulas for the reactants and products
Changes the rate of a chemical reaction but can be recovered unchanged
In many reactions as soon as the products begin to form they immediately do what?
Begin to react with each other in and reform the reactants.
A reverse what can occur?
A reverse reaction may occur to a greater or lesser degree than?
Original reaction;depending on the specific reaction and the conditions.
Chemical reaction in which the products reform the original reactants
Quantitative information revealed by a chemical equation
The coefficients of a chemical reaction indicate relative, not absolute, amounts of reactants and products; relative masses of the reactants and products can be determined from the reactions coefficients; reverse reaction for a chemical equation has the same relative amounts of substances as the forward reaction.
Mechanical equation usually shows the smallest number of atoms molecules or ions that will satisfy what?
Law of conservation of mass in a given reaction.
Chemical equations provide useful quantitative information however there is also important information that what?
That is not provided by a chemical equation.
An equation gives no indication of weather a reaction will what?
Occur or not
Chemical equation gives no information about the speed of what? bonding?
At which reactions occur or about how the bonding between atoms or ions changes during the reaction
balancing chemical equations
Identify the names of the reactants and the products and write a word equation, write a formula equation by substituting correct formulas for names of reactants and products, and balance the formula equation according to the law of conservation of mass, count atoms to be sure that the equation is balanced.
the trial and error method of balancing equations is made easier by use of following guidelines:
Balance different types of atoms one at a time, first balance atoms of elements that are combined and that appear only once on each side of the equation, balance polyatomic ions that appear on both sides of the equation as single units, balance hydrogen and oxygen atoms after atoms of all other elements have been balanced.
Coefficients should be divided by their greatest common factor in order to obtain the smallest possible what?
Whole number coefficients
How to avoid the most common mistakes when balancing equations:
Avoid writing in correct chemical formulas for reactants or products and trying to balance an equation by changing the subscripts
Subscripts cannot be what?
Not be added deleted or changed
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