Acids and Bases 8.1-8.4 Flashcards
What did Antoine Lavoiser think?
He believed that oxygen was present in all acids. He gave them the name ‘oxygene’, these theory was key disproving the phlogiston theory but was wrong. This was proved wrong when they discovered the acid HCL, and realised that it was hydrogen not oxygen that was essential.
What is an acid? Arrhenius’s theory
A substance that ionises in water to produce hydrogen ions.
What is an alkali? Arrhenius’s theory
A substance that ionises in water to produce hydroxide ions.
What is a neutralisation reaction?
The combination of an acid and a base, involving the combination of a hydroxide and a hydrogen ion.
What is the Bronsted - Lowry theory?
They referred to a hydrogen ion as a proton, and therefore an acid could be referred to as a proton donator and an alkali as a proton acceptor. A Bronsted - Lowry acid is therefore one that donates a proton and a Bronsted - Lowry base is one that accepts a proton.
What is a hydronium ion?
The hydronium ion H3O+ is formed when water forms a coordinate bond with water.
What is a conjugate acid - base pair?
A conjugate acid base pair differ by one proton. So water H30+ is the conjugate acid, H20 is therefore the conjugate base. But water also has an OH- ion so we can say that water is amphiprotic.
What is an amphiprotic species?
Substances that can act as either a Bronsted - Lowry base or a Bronsted - Lowry acid. For example water, which can be both H30+ or OH-. Amino acids also act as an amphiprotic species, because they can be both acidic or alkaline with the zwitterion form in the middle.
What colour does phenolphthalein turn in acids and alkalis?
Acids - colourless
Alkali - pink
What colour does methyl orange turn in acids and alkalis?
Acids - red
Alkalis - yellow
What does an acid and a metal/metal oxide/hydroxide/hydrocarbonates/carbonates form?
A salt.
Which reactions with acids form a salt and hydrogen?
Metals above hydrogen in the reactivity series.
What do acids and metals above hydrogen in the reactivity series form?
A salt and hydrogen.
What is the standard enthalpy change of neutralisation?
The energy change when one mole of water from the reaction between a strong acid and a strong base is formed under standard conditions.
How does calcium oxide react with aqueous acids?
Calcium oxide does not react directly with aqueous acids. This base dissolves in water to create an alkaline solution of calcium hydroxide, which neutralises, the acid:
CaO + H20 - Ca(OH)2
Calcium hydroxide is slightly soluble in water and therefore an alkali.
What does a metal carbonate/metal hydrocarbonate and an acid produce?
Salt and carbon dioxide and water.
What is the difference between amphiprotic and amphoteric?
Amphiprotic substances refers to the Bronsted - Lowry definition of an acid and a base, and suggests that the substance can both have ions able to donate and accept a proton. Whereas amphoteric is a more general term and refers to the quality of a substance to react with both an acid and a base. All amphiprotic substances are amphoteric but not all amphoteric substances are amphiprotic.
What is the difference between the Bronsted - Lowry definition of an acid and the Lewis definition of an acid?
The Bronsted - Lowry definition defines an acid as a proton donor, whereas the Lewis definition defines it as an electron pair acceptor, so it is the reverse. The bases are the opposite, an acceptor by the Bronsted - Lowry definition and a electron pair donor via the Lewis definition. The Lewis definition is more general than the Bronsted - Lowry and can be applied to reactions that do not include the transfer of protons. The Lewis definition covers all the Bronsted - Lowry reactions because the acceptance of a proton by a base must involve the donation of an electron pair to the proton. For example the reaction between BF3 and NH3 is a Lewis reaction but not a Bronsted - Lowry one.
NH3 + BF3 = N3H:BF3
This involves the transfer of electrons but not the transfer of a proton.
What is a Lewis base acid reaction?
This is the transfer of a pair of electrons and can involve things like forming a complex ion, which makes it a more general definition than the Bronsted - Lowry one. A coordinate or dative bond is always formed in a Lewis acid base reaction.
Fe2+ + 6H2O = (Fe(H2O)2)2+
The transition metal accepts electrons, getting a less positive charge and therefore is the Lewis acid. The water donates electrons and therefore is the Lewis base.
What makes something a Lewis acid or a Lewis base?
For a substance to act as a Lewis base, it must have a lone pair of electrons. For a substance to act as a Lewis acid it must have the ability to accept a lone pair of electrons.
How do you make a salt from an acid?
The hydrogen atom in the acid can be seen as replaceable, and can be replaced by a metal ion to form a salt if it is more reactive than hydrogen.
How does an acid react with a metal?
Metal + acid = salt + hydrogen
How does an acid react with a carbonate or a hydrocarbonate?
Acid + carbonate/hydrocarbonate = salt + carbon dioxide + water.
How does an acid react with an alkali?
Base + acid = salt + water
This is a neutralisation reaction and usually involved the combination of a H+ ion and a OH- ion. Neutralisation reacts are usually exothermic.
