8.2 Flashcards
What is an alkali?
Alkalis are bases that dissolve in water to form the hydroxide ion OH-
What types of compounds are included in alkalis?
Metal Oxides and Hydroxides
Ammoina
Soluble carbonates ( Na2CO3 and K2CO3) and hydrogencarbonates (NaHCO3 and KHCO3)
with what compounds do acids react with to form salts?
metals, bases, and carbonates
what is a salt?
Salt is an ionic compound formed when the hydrogen of an acid is replaced by a metal or another positive ion.
what are parent acids/bases?
those terms are sometimes used to describe the relationship between an acid, a base, and their salt.
Acid + reactive metal =
Salt + hydrogen
In what cases will the acid + reactive metal reaction proceed?
only if metal is more reactive than hydrogen ( the reactivity is presented in the data booklet)
what are spectator ions?
Species which do not change during a reaction and can be cancelled out.
What are the states of compounds included in the reaction of acid + metal ?
All metals - solid
all acids - aqua solution
salt - solid / if possible to dissolve - aqua solution
hydrogen - gas
Acid + base =
What is the name of this reaction?
salt + water
neutralization reaction
What is a neutralization reaction?
Neutralization reactions occur when an acid and base react together to form a salt and water. They are exothermic.
What is enthalpy of neutralization?
enthalpy change when acid and base react to form 1 mole of water
For reactions between all strong acid and bases the enthalpy is very similar to what? and why?
delta H = -57 KJmol-1
because net reaction is the same - involving the formation of water to form its ions.
What can neutralization reactions be useful for?
To help reduce the effect of an acid/base
Acid + carbonate =
salt + water + carbon dioxide
what is effervescence?
The reactions like acid + carbonate or acid + metal involve a gas being given off so they visibly produce bubbles, known as effervescence
What is an indicator?
chemical detectors, giving info about a change in the environment
What is an Acid-base indicator?
an indicator that changes colour reversibly according to the concentration of H+ ions in the solution
How are indicators usually used?
either as aqueous solutions or absorbed onto test paper
indicators and their colours
litmus - pink in acid - blue in alkali
methyl orange - red - yellow
phenophthalein - colourless - pink
What is universal indicator?
mix of several indicators
what are acid- base titrations based on?
neutralization reactions
what are neutralization reactions often used for
to calculate the exact concetration of an acid/alkali when the other concentration is known
the process of acid-base titration:
- reacting together a carefully measured volume of one of the solutions
- adding the other solution gradually
- until the equivalmnce point ( where they neutralize each other)
what is a good indicator?
the one that gives a distinct or sharp colour change at the equivalence point
