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pH =-log.of 10 to power -1,this is 1
pH=-log of 10 to power -3
pH= 4,pH=5,pH=7,pH=8,.....pH=14.
these are all different pH values.
what you understood?
the PH values getting an increment of 1.
so many people do not sense pH =2,pH=3,
2 and 3 has a gap of 10 times.
that's what measurely i wanted to tell,so i will go for that
just weigh a minute .
this how we get it ? number one.
number two,if we know pH values,if suppose pH=x,we are some time asked to write reverse.
so,you can write that by H ion concentration,H ion = x,and you are asked to know what is H ion concentration?
then write,H ion = 10 raised to -x,so for this if you think reverse,by this form H ion=10 raised to this x,-x.this is how you will re write the reverse concentration of H ion.
ok,now very important thing,
why i taught all these thing?these are the basics which one should know from the 11th class.
ok, now in 12th class as i have written Kw =H ion and OH ion product giving 10 to power -14.
i want to apply this method on this relation.
ionic product of water.let us take the negative log. n both side.
-logKw =-log. of H ions and -log. of OH ions.
if you are not very comfortable let me put them in bracket and keep this + as it is .
here,and - log. of 10 raised to -14.
what i call this in short Pkaw that discussion.
= this i will call PH .this i will call POH .this i will say - of - 14 log10.i can simplify this relation as Pkaw= PH + POH.
=14,this relation is very very important.
how many people understood?
Now, you can say that what you have written here
I had written the logarithmic form of ionic product of water.
Understood ? All what temp. 5ÂșC.one important point after this.
whenever we have a ,please be very care full and listen.neutral water or plane water there is no meaning of neutral water or acidic water
if it is neutral,what is the meaning of neutral?it is non acidic and one thing is also sure its not basic.
what does this mean?
it has no H ion it has no OH ions.is that the meaning, no
because i told you any kind of water that has H ions,OH ions ,water,
so, by saying this ,i am saying something wrong,
then how it could be neutral?
it is that its acidic behavior causing particles are cancelled by the basic behavior causing particles
that means the H ions and OH ions concentrations are equal.
its not that they are absent ,they are present but they cancel out each other.
if this two number are equal then we can re write this expression like this H ions multiplied by OH ions,10 to power -14,i can re-write this expression
say that this is x,this is also x then it is x*x*10 =raised to power-14 ,this is Kw,
i can say that x square is 10 to power -14 or Kw .so i can say x is square root of Kw.
or this is 10 to power -7.
how many understood?that means in this glass of water
i will tell few things ,what is this ?1. this is at 25 degree celcius ,my assumption.
ok,in this water H2O molecules are there ,there are H ions ,there are OH ions.now these H ions in it IS 10 TO POWER -7,OH ions in it 10 to power -7 molar.
what happened ?H ion and OH ion are equal.if these are equal,what is it?neutral if this neutral i can drink.
no ,not acidic
not basic,
do not worry about it
well now the points comes ,please this is true with water but what if i take the acids?then the ans. simple.whenever we add acid ,suppose there is an acid HA,i am adding this ,so it ionizes ,i told that this proton
this proton is actually ,angry proton is the reason for acidity
let the water be there , water is giving H ions and OH ions.
ok ,now just imagine ,these two are equal in number .
and there is equilibrium .
and i added HA, it has given me H ions
now total H ions is surely greater than OH ions.i can say that this H ions number is greater than OH ions. i can prove that .
how?let me say that there are 10 to power -7, this is 10 to power -7.
i added here a moles of H ions ,the lechatelier principle say that ,i need not tell that again repeatedly
that whenever you add product ,the equilibrium will shift to backward direction.
ok, this backward movement will swipe some of the H ions ,you assume some number ,let me say that y number of H ions are swept here.
but H ions alone will never come
they will also take up equal OH ions for bonding
so, what happened the final value left is ,tell me 10 to power -7 minus y plus a, very good.
and here 10 to power -7 minus y,so this tells that a is a non zero quantity yesterday i told that chemist never use
zero acid ,zero books ,zero pen they always use some thing which physically exist .so positive values ,so a>0 value
if it is added physically means it exist it has greater than values
so,what you find?this is greater than this term.
so, i can say that whenever we add acid H ions are dominating in number over OH ions
this relation exist
ok, if do the reverse of it ,i will not like to mention that here you can guess mentally
for few people let me write it
tell fast ,ok BOH let me say base ,basic is reversible with H and OH ions.now tell
10 to power -7 ,10 to power -7 ,say this B amount is added ,now some Y amount is lost 10 to power -7 minus y,
in the backward direction of equilibrium shift,same weight is here ,but is an extra term added to
OH ions ,so, what you found the OH ions concentration is greater than that of H ions.
well now i am going to that important part which