1
Q
properties of chemical reactions
A
- new substances are formed
- bonds in reactants are broken (endothermic change – absorption of energy)
- bonds in products are created (exothermic change – release of energy)
- stoichiometry
2
Q
stoichiometry
A
- fixed relationship between the particles of the reactants and products ⇒ no overall change in mass
- the simplest ratio of the number of moles of reactants and products in a chemical reaction
- the balancing numbers are known as the coefficients of the reaction
3
Q
types of chemical reactions
A
- synthesis reaction: A + B → AB
- decomposition reaction: AB → A + B
- single-replacement reaction: A + BC → AC + B
- double-replacement reaction: AB + CD → AD + CB
- neutralization reaction: HA + BOH → BA + H2O (acid + base → salt + H2O)
- combustion: X + O2 → XO
- polymerization
- redox reaction
4
Q
limiting reactant/reagent
A
= the reactant which will completely react, leaving other reactants unused, which will be left behind and is said to be in excess
5
Q
titration
A
- = chemical technique in which one solution is used to analyze another solution to find its concentration or amount
- form of volumetric analysis
- analyte = substance that is being analyzed, usually has an unknown concentration
- titrant = solution with a known concentration (in the burette)
- equivalence point ⇒ stoichiometric equivalence of reactants and products; acid is completely neutralized
- endpoint ⇒ color change
6
Q
acid-base indicators
A
- protonate or deprotonate in acidic/basic conditions ⇒ change their color
- phenolphthalein: acidic → transparent, basic → purple/pink
7
Q
back (indirect) titration
A
= technique used to determine the amount of a weak acid or base present in an impure sample
the analyte reacts with a strong acid/base, the excess is then titrated against a strong base/acid
8
Q
when is back titration used
A
one of the reactants is volatile
an acid or base is an insoluble salt
a particular reaction is too slow
direct weak acid against weak base titration
