chem feb unit test
synthesis reaction
1+1=2
making a new compound
combustion reaction
oxygen combines with a substance and releases energy in the form of heat and light. can be combustion and synthesis
decompostion reaction
2=1+1
often requires an energy source, opposite of synthesis
single displacement reaction
1+23=13+2
when the atoms of one element replace the atoms of another element in a compound.
single displacement rule
metal replaces metal, below on activity series
double displacement reaction, what does it make?
12+34=14+23
exchange of ions between two compounds, all produce a precipitate, gas or water
stoichiometry
the study of quantitative relationships between amounts of reactants used and products formed by a chemical reaction. based on law of conservation of mass (matter is neither created nor destroyed in chem rxn)
another way to say conservation of mass
the total mass of all reactants and the total mass of all products in a chemical reaction must be equal
what is stoichiometry used for
to determine how much of each reactant is needed for a specific reaction, or how much of each product will be produced in the reaction
what two things do coefficients represent
number of individual particles and number of moles
limited/excess reactants
generally, one or more reactants are in excess (more than you need), while one is limited. the reaction continues until all of this limited reactant is used up. thus, the amount of product depends on the reactant that is limited
theoretical yield
maximum amount of product that can be produced from a given amount of reactant. (in theory, on paper)
actual yield
the amount of product actually produced when the chemical reaction is carried out in an experiment
how might the theoretical and actual yield differ
side reactions can occur (lose some of desired product), products can turn back into reactants, reaction doesn't go to completion
percent yiled
the ration of the actual yield to the theoretical yield, expressed as a percent.
percent= actual/theoretical x100
empirical formula
the formula with the smallest whole number ratio of the elements in compound. may or may not be the same as molecular formula
molecular formula
actual number of atoms of each element in one molecule of formula unit of the substance
chemical reaction
the process by which the atoms of one or more substances are rearranged to form different substances
chemical equations
shows a reactions reactants (starting substances) and products (substances formed in rxn)
word equation vs skeleton equation
- uses words to describe the chemical equation, unbalanced
- uses chemical formulas and arrow to describe the chemical equation, unbalanced
what do word and skeleton equations lack
law of conservation of mass (balanced)
balanced chemical equations
shows how the law of conservation of mass is obeyed. show that the number of atoms of each reactant and each product is equal on both sides of the arrow