Stoichiometry

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Stoichiometry	The study of relative amounts, ratios, of substances involved in chemical reactions
A balanced chemical equation indicates	Mole ratio of reactants and products (the relative number of molecules participating in a chemical reaction)
A balanced chemical equation does not indicate	The rate of a reaction The extent of a reaction Requires or gives off heat What temperature or pressure is needed How individual atoms or molecules are transformed from reactants to products
Mass-mass stoichiometry	Calculating the mass of one substance in a reaction by using the equation and mass of one of the other substances -write balanced equation (known and unknown) -change known mass into moles -molar ratio used to predict moles -change the moles into mass
Limiting reactant	The reactant completely used up Determines the amount of product formed
Excess reactant	Any unreacted reactents
Mass-concentration stoichiometry	Two solutions may be mixed to form a precipitate or solids may dissolve in some solutions to form new products Same steps as mass-mass but using the formula n=cV
Gravimetric analysis	Quantitative analysis by mass
Weighing to constant mass	A repetitive cycle of heating and weighing the sample until no further decrease in mass is detected
Alkalinity	A measure of how well a body of water is able to resist changes in pH and therefore withstand acid pollution
Buffers	Some solutes in water can act to resist changes in pH0
Volumeteric analysis	Measured volumes of solutions where one is an accurately known concentration and the unknown concentration of the second solution can be determined using stoichiometry
Solution stoichiometry	Involves reactions in solution such as precipitation reactions and the neutralization of an acid and a base
Acid-base titrations	Experimental technique used for volumetric analysis based on neutralisation reactions where the unknown concentration of a solution is determined by reacting it with a solution of known concentration
Standard solution	A solution of known concentratiotn Prepared by dissolving an accurate amount of solute in water using a volumetric flask calibrated to contain the specific volume
Burette	Instrument used to deliver definite but variable volumes of liquid
Titre	The volume of liquid measured by the burette
Aliquot	A known volume of liquid delivered by a pipette
Equivalence point	Point at which chemically equivalent amounts of acid and base are present (according to equation)
End point	Point at which the indicator changes colour usually about one drop after equivalence point but only if carefully chosen to make sure that it is close to the equivalence point
Concordant	Titres within 0.05 mL of each other
Primary standard	Pure substances that: -have a high state of purity -accurately known formula -stable (not change over time during storage or a reaction with the atmosphere) -cheap & readily available - high molar mass so that weighing errors are minimised
Indicators	Substances that have different colours depending on the pH of their surroundings

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	Erstellt von Minoshka Bocarro vor etwa 8 Jahre