Understanding Acids and Bases: Definitions, Properties, and Reactions Explained

one of the most important things that we learned in grade 11 was how to define an acid and how to define a base so I've

given you the bronze dead Lowry or the Lowry Bron stead definitions here of an acid and a base there is another

definition that you need to know which I'll go over in a second but this is the more accepted or the one that we refer

to most commonly nowadays an acid is a proton donor so when we say protons we mean an H+ ion this over here is a

proton so an acid is a proton donor in other words it gives away an H+ and a base is a proton acceptor something else

that I wrote here that is important to note it's just the terminology that we use acids ionize so an acid can ionize

in water bases dissociate I'll explain the slight difference in a second but first here's a list of common acids so

their name their chemical formula and also their strength so if they're strong or weak and you need to remember

sulfuric acid is h204 and it's strong you need to know that sulfuric acid is strong you need to know that

hydrochloric acid is strong you need to know that ethanoic acid or acetic acid is weak these are things that you must

study and what do I mean by weak or strong I will also revisit that in a lesson here are some common bases same

thing the name I've also given the common name in Brackets the formula and if they are generally considered to be

strong bases or weak bases again these are things that you need to study if we say ammonia you need to know that

ammonia is NH3 and you need to know that it is considered to be a weak base so remember I told you that there were two

ways that we can Define acids and bases the first definition is called the arenus definition and I've pasted the

definitions over here for you you do need to know this we can ask this as a definition so arenus defined an acid as

a substance that produces hydrogen ions okay there's the proton H+ ions or hydronium ions when they dissolve in

water and a base is a substance that produces hydroxide ions when they are dissolved in water this definition is

fine it still holds up in most cases but the issue with this definition is that it limits acids and bases to aquous

Solutions only remember Aquis is when I dissolve it in water or when it reacts with water it also limits bases to hyd

oxides so bases that have o minus ions in it but we do know that there are bases for example ammonia NH3 which is a

base it's a weak base it does not have oh minus ions in it so that is an important thing to note this definition

is good it exists you must learn it but it has some limitations here is a reaction equation that shows what

happens when an acid so in this case it's hydrochloric acid reacts with water and it forms Al hydronium ions so

there's our h3o plus ions as well as a chloride ion I'll explain again where we get this from how do we know that it

forms these things it's important that you are able to complete an equation like this and my bottom equation is an

example of a base dissociating in water so it's breaking up into its ions and you can see here it's NaOH sodium

hydroxide and it breaks up or dissociates into na+ ions and O minus ions there's the hydroxide and that is

where this definition comes from then we've got the bronze dead Larry or the Larry bronze dead definition or Theory

and they said that an acid is a proton donor in the presence of a base which means that the acid will give away an H+

ion and a base is a proton acceptor in the presence of a base so the one gives away the one accepts that's also why

it's called a proton transfer or a protolysis reaction remember the proton in this case is H plus so they're

transferring the proton so the characteristic properties of acids so what gives acids their properties can be

attributed or ascribed to the H atoms in their compound so it means that because of these H+ atoms because of these um

protons that's what gives atoms their properties so when an acid is diluted with water a chemical reaction occurs

it's known as ionization and we form hydronium ions so generally when we think of hydronium ions h3o plus ions we

think of acids when we think of hydroxide ions we generally think of bases so the formation of hydronium ions

is basically when the proton the H+ ion reacts with H2O and here we go what makes a base a

base what is responsible for the Basel likee Properties or the alkaline properties is the formation of the

hydroxide ion the O minus ion and just by the way sometimes you hear that bases are called alkal substances so a base

that is soluble in water is called an Alkali that's where that word comes from so bases NaOH dissociate or break up in

water and this is the equation I showed you earlier it's aquous because it's dissolved in water it's the ions

dissolved in water and this is very important so bases generally dissociate which means that they break up into

their ions but this weak base called ammonia actually ionizes the reason why this one is called dissociate and this

one is called ionize is because over here the one that dissociates breaks up into its ions these are ionic substances

so it consists of a metal which is the sodium ion na+ and O minus the anion so bases generally dissociate because

generally they are ionic however ammonia NH3 is actually a coal bonded compound so it doesn't dissociate or break up

into ions cuz it's not ionic it's coent so it actually reacts with the water and it forms nh4+ an O minus and remember

this is all about a proton transfer so acids are proton donors one of the H is from the water the water is acting like

an acid okay waterers on water is known as ailite it can sometimes be an acid sometimes be a base I know that can

confuse people but in this case it's acting like an acid and it donates the proton so it gives

away one of its H+ to the base so think about it H2O it loses an H+ so now it's no longer

two hydrogens it's got one hydrogen it was neutral it lost a positive so it's got a negative charge that's where the O

minus comes from and that H+ is given to the base remember bases are proton ACC receptors it was NH3 it becomes nh4

because it got an extra H+ so again there's a lot going on but this is basically a summary showing why

acids ionize so it is a polar calent substance it ionizes in water so it reacts with water and in this case it's

forming CL minus and h3o+ remember when you see H3 plus you think about acids it says your strong

acids ionize completely in water and this is the definition of a strong acid it is something that you learned in

grade 11 it is something that you need to know in grade 12 as well so what happens is acids are proton donors it

gives away the h plus it gives away an ion and donated to the base that's why the base was

H2O it becomes h3o plus why does it become plus because it gains a proton which is a positively

charged thing then it was HCL but it's now lost a proton it's lost an H+ so it's no longer HCL it is now just CL and

it's a minus because it lost a plus very very important and we will discuss this later but HCL is a strong acid which

means that the equilibrium lies far to the right it means that there will be a very high concentration of hydronium

ions so if I know the concentration of the acid I will therefore know the concentration of the hydronium ions and

this becomes important when we calculating pH later and as I said bases dissociate which means that they

dissociate or they break up they ionize ionic separates in water becomes na+ and O minus because this is a strong base it

forms a high concentration of hydroxide ions so if I know the concentration of the base I immediately know the

Concentra of the hydroxide ions and this will be important when calculating the pH of bases later on and just remember

the exception in this case the weak base which is ammonia it's not ionic doesn't consist of ions it's co valent so it

doesn't dissociate it ionizes slight slight slight difference but it is important to know that is our first

recap lesson on grade 11 aets and bases in the next recap lessons we'll go over other important terminology and things

that you learned in grade 11 but you need to know in grade 12 bye everyone