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Chem 121 Chapter 4
Chemistry 121
28
Chemistry
Undergraduate 1
11/04/2013

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Term
stoichiometry
Definition
fundamentals of chemical calculations which loosely translates as "the measure of the elements."
Term
mole
Definition
allows chemist to scale up from the atomic/molecular level to the laboratory scale.
Term
What are two things you need to be successful in using analysis calculations?
Definition
1. acknowledge of the equalities that can be made into conversion factors.
2. a logical sequence of steps to guide us from the starting set of units to the desired units.
Term
molecular mass (sometimes called molecular weight)
Definition
The sum of the atomic masses (in u) of all of the atoms represented in a molecular chemical substance.
Term
molar mass
Definition
the mass of one mole of a substance
Term
Avogadro's Number
Definition
6.022 x 10^23 The units of the chemicals can be atoms, molecules, formula units, and so on.
Term
chemical compounds
Definition
Within chemical compounds, moles of atoms always combine in the same ratio as the individual atoms themselves.
Term
mass-to-mass calculations
Definition
mass of A -> moles of A -> moles of B -> mass of B
Term
percentage composition
Definition
percentage by mass
Term
percentage by mass
Definition
the number of grams of an element combined in 100g of a compound.
Term
Percentage by mass of element=
Definition
(mass of element/mass of whole sample) x 100%
Term
molecular formula
Definition
the formula that gives the composition of one molecule
Term
empirical formula
Definition
the simplest ratio of the atoms of each element in a compound
Term
Why is the law of conservation of mass and its use with percentage composition is important?
Definition
it allows us to determine the amount of three substances using only two experiments
Term
combustion reaction
Definition
a reaction in which a compound burns completely in pure oxygen
Term
what are the sole products of a combustion reaction?
Definition
carbon dioxide and water
Term
Combustion Analysis
Definition
a method for obtaining percentage composition data for organic compounds
Term
What are the diatomic molecules?
Definition
Hydrogen
Nitrogen
Oxygen
Fluorine
Chlorine
Iodine
Bromine
Term
What are the steps in solving a limiting reactant problem?
Definition
1.identify a limiting reactant problem by the fact that the amount of more than one reactant is given.
2.identify which is the limiting reactant, pick one of the reactants and calculate how much of the second reactant is needed. If the amount calculated for the second reactant is less than what is given, there is an excess of the second reactant and therefore the first reactant is limiting. If the calculated amount of the second reactant is more than what was given, then is will be consumed first and the second reactant is limiting.
3.solve the problem based on the amount of the limiting reactant at hand. For the final calculations we must use the amount of the limiting reactant given in the statement of the problem.
Term
limiting reactant
Definition
limits the amount of product that is formed
Term
excess reactant
Definition
the reactant left over once the limiting reactant is used up
Term
competing reaction
Definition
a reaction that reduces the yield of the main product by forming by-products
Term
by product
Definition
the substance made by a reaction that competes with the main reaction
Term
main reaction
Definition
the desired reaction between the reactants as opposed to competing reactions that give by-products
Term
actual yield
Definition
how much is isolated of a desired product. An experimentally determined quantity
Term
theoretical yield
Definition
what must be obtained from a product if no losses occur. a calculated quantity based on a chemical equation and the amounts of the reactants available.
Term
percentage yield
Definition
the actual yield calculated as a percentage of the theoretical yield
Term
percentage yield=
Definition
actual yield/theoretical yield x 100%
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