Chapter 6:Chemical Reactions: Mole and Mass Relationships
Atomic mass of an element is the average mass of the element’s atoms.
The molecular mass of a molecule is the average mass of a substance’s molecules.
Numerically, a substance’s molecular mass (or formula mass for an ionic compound) is equal to the sum of the atomic masses for all the atoms in the molecule or formula unit.
Samples of different substances always contain the same number of molecules or formula units whenever their mass ratio is the same as their molecular or formula mass ratio.
One mole of any substance is the amount having a mass in grams—its molar mass—numerically equal to its molecular or formula mass in amu.
One mole of any substance, contains 6.022 * 10^23 formula units, a value called Avogadro’s number.
There are four steps for determining mass relationships among reactants and products:
STEP 1: Write the balanced chemical equation.
STEP 2: Choose molar masses and mole ratios to convert the known information into the needed information.
STEP 3: Set up the factor-label expressions.
STEP 4: Calculate the answer and check the answer against the ballpark estimate you made before you began your calculations.
The reactant that is exhausted first in a reaction (oxygen, in the case of the candle) is called the limiting reagent. The amount of product you obtain if the limiting reagent is completely consumed is called the theoretical yield of the reaction.
The amount of product actually obtained—the reaction’s actual yield—is somewhat less than the theoretical yield. The amount of product actually obtained in a reaction is usually expressed as a percent yield.
Percent yield = (Actual yield/ Theoretical yield) * 100
Atomic mass of an element is the average mass of the element’s atoms.
The molecular mass of a molecule is the average mass of a substance’s molecules.
Numerically, a substance’s molecular mass (or formula mass for an ionic compound) is equal to the sum of the atomic masses for all the atoms in the molecule or formula unit.
Samples of different substances always contain the same number of molecules or formula units whenever their mass ratio is the same as their molecular or formula mass ratio.
One mole of any substance is the amount having a mass in grams—its molar mass—numerically equal to its molecular or formula mass in amu.
One mole of any substance, contains 6.022 * 10^23 formula units, a value called Avogadro’s number.
There are four steps for determining mass relationships among reactants and products:
STEP 1: Write the balanced chemical equation.
STEP 2: Choose molar masses and mole ratios to convert the known information into the needed information.
STEP 3: Set up the factor-label expressions.
STEP 4: Calculate the answer and check the answer against the ballpark estimate you made before you began your calculations.
The reactant that is exhausted first in a reaction (oxygen, in the case of the candle) is called the limiting reagent. The amount of product you obtain if the limiting reagent is completely consumed is called the theoretical yield of the reaction.
The amount of product actually obtained—the reaction’s actual yield—is somewhat less than the theoretical yield. The amount of product actually obtained in a reaction is usually expressed as a percent yield.
Percent yield = (Actual yield/ Theoretical yield) * 100
