anonymous
  • anonymous
Please help me with few Acid Base questions!
Chemistry
  • Stacey Warren - Expert brainly.com
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SOLVED
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schrodinger
  • schrodinger
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anonymous
  • anonymous
anonymous
  • anonymous
in the image i understand NR9 , but not 27, 28 and NR 10 beacuse I am not sure how to make the eqaution from looking at the question
caozeyuan
  • caozeyuan
let HA be an acid and A- be the conjugate base after dissociation and assume the solvent is water

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caozeyuan
  • caozeyuan
therefore we have the following equation\[HA \rightarrow A ^{-}+H _{3}O ^{+}\]
caozeyuan
  • caozeyuan
Now, Ka is just the equilibrium constant of this equation
caozeyuan
  • caozeyuan
understood?
anonymous
  • anonymous
not really
caozeyuan
  • caozeyuan
well, acid dissociates in water to form the conjugate base and hydronium according to the equation above. I hope your teacher told you what is the conjugate base of an acid. If not, the easiest way to think of it is to rip off the proton and whatever left is the cb
anonymous
  • anonymous
then will the eqaution look like Nan3 + h20= H30 + ??? somthng like this?
caozeyuan
  • caozeyuan
We know that any equilibrium has a constant K which is a ration of forward versus reverse reaction.\[aA+bB \rightarrow cC+dD\]\[\frac{ A^{a} B^{b}}{ C ^{c} D ^{d}}\]
caozeyuan
  • caozeyuan
you should use HN3, not NaN3 because NAN3 is not acid so it cannot protinate water
caozeyuan
  • caozeyuan
so we have HN#+H2O=H3O+ + N3-
caozeyuan
  • caozeyuan
H2O is left out in the Ka expression because solvent is not part of the equilibrium expression
anonymous
  • anonymous
then why does it give NaOH concentration in NR 10?
caozeyuan
  • caozeyuan
Because NaOH is used to neutralize HN3
anonymous
  • anonymous
damn this is just confusing then how would u slow it when Naoh is not in the equation we made
caozeyuan
  • caozeyuan
Lets get Q27 out first, ok?
anonymous
  • anonymous
okey
anonymous
  • anonymous
I can do that one looking at the eqatuion so I am fine with that question
caozeyuan
  • caozeyuan
So Ka is the acid dissociation constant, which is a special case of equilibrium constant, did your teach laugh you these terms?
anonymous
  • anonymous
yes
caozeyuan
  • caozeyuan
OK, so you should know product over reactants, constants are powers, stuff like that, right?
anonymous
  • anonymous
yes easy
caozeyuan
  • caozeyuan
Great, so what is the dissociate reaction of HN3 with H2O?
anonymous
  • anonymous
what do u mean
caozeyuan
  • caozeyuan
\[HN _{3}+H2O \rightarrow H3O ^{+}+N _{3}^{-}\]
caozeyuan
  • caozeyuan
I mean this equation
anonymous
  • anonymous
ok what do u want me to do
caozeyuan
  • caozeyuan
write the expression for Ka of this reaction
anonymous
  • anonymous
I would say the answer is B
anonymous
  • anonymous
since liquids dont coiunt
caozeyuan
  • caozeyuan
Fantastic! 27 solved! You still have problem with 28?
anonymous
  • anonymous
yes
anonymous
  • anonymous
wait first of all
anonymous
  • anonymous
I have to remeber that theory u told me right when making thses eqautions
caozeyuan
  • caozeyuan
you just did it right
anonymous
  • anonymous
no i am talking about the ionic eqaution
caozeyuan
  • caozeyuan
Well acid donates proton to water to form hydronium ion and conjugate base
caozeyuan
  • caozeyuan
makes sense?
anonymous
  • anonymous
alright lets move on
caozeyuan
  • caozeyuan
In this case, HN3 is acid, H2O is water, H3O+ is hydronium and N3- is conjugate base
caozeyuan
  • caozeyuan
OK, 28 is simple. remember this: if the numeric value for Ka is less than 1, bottom is larger, if it is bigger than i top is larger
caozeyuan
  • caozeyuan
there is no chemistry, only math
caozeyuan
  • caozeyuan
it's like say 5/7 is less than 1, why? because bottom is large. 7/5 is larger than 1 because top is large
anonymous
  • anonymous
answer is A?
caozeyuan
  • caozeyuan
Back to chem, bottom is reactant, top is product, so which side has higher concentration?
caozeyuan
  • caozeyuan
let's not jump too fast
anonymous
  • anonymous
why is there no sigh of H30
caozeyuan
  • caozeyuan
is Ka larger or smaller than 1?
anonymous
  • anonymous
yes
caozeyuan
  • caozeyuan
Ka is smaller than 1, right?
anonymous
  • anonymous
yes
caozeyuan
  • caozeyuan
so which side has higher concentration?
anonymous
  • anonymous
bottn is larger
anonymous
  • anonymous
hold up its B!
caozeyuan
  • caozeyuan
Great!
caozeyuan
  • caozeyuan
Now, onto calculation
anonymous
  • anonymous
i understand nr9 , nr10 is confusing
caozeyuan
  • caozeyuan
lets start with basics
caozeyuan
  • caozeyuan
how many moles of Hydronium can 1 mole of HN3 produce?
caozeyuan
  • caozeyuan
solvent is 1L of H2O of cuz
anonymous
  • anonymous
okay
caozeyuan
  • caozeyuan
how many moles of Hydronium can 1 mole of HN3 produce?
anonymous
  • anonymous
not sure.....
caozeyuan
  • caozeyuan
\[K _{a}=x^2,x=\left[ H3O+ \right]\]
anonymous
  • anonymous
o yea i know that eqaution wait r u trying to do nr9?
caozeyuan
  • caozeyuan
No, but we need this info to do 10
anonymous
  • anonymous
oh
anonymous
  • anonymous
k i already foinf the ph its 2.64
caozeyuan
  • caozeyuan
so we have 10^-2.64 mole of H3O+, right?
anonymous
  • anonymous
yes
caozeyuan
  • caozeyuan
how many mole of HN3 is 2.2kg?
anonymous
  • anonymous
51.15089514
caozeyuan
  • caozeyuan
Great, but three digit is enough for your question
anonymous
  • anonymous
ok
anonymous
  • anonymous
why did they give conc for naoh?
caozeyuan
  • caozeyuan
If we have n moles of HN3, we can produce N*10^-2.64 mole of H3O+
caozeyuan
  • caozeyuan
which means we need this many mole of NaOH to completely neutralize
caozeyuan
  • caozeyuan
molar concentration=mole/liter, right?
anonymous
  • anonymous
yes
caozeyuan
  • caozeyuan
we have two of three, can you solve the third?
caozeyuan
  • caozeyuan
that's why we need conc of NaOh
anonymous
  • anonymous
we already have the conce its 6.00 mol/l given in the question
caozeyuan
  • caozeyuan
Yes, and we know the mole, right?
anonymous
  • anonymous
8.585
anonymous
  • anonymous
wait i am confued ususaly we have an eqaution when we dod these kind of question
caozeyuan
  • caozeyuan
Now, can you solve for the liter
anonymous
  • anonymous
that is in liter
caozeyuan
  • caozeyuan
I am not sure what are you confused about
anonymous
  • anonymous
where is the eqaution?
anonymous
  • anonymous
like Naoh+hn3?----?
caozeyuan
  • caozeyuan
NO!, you don't need that
caozeyuan
  • caozeyuan
a molar is 1mole over 1 liter
anonymous
  • anonymous
becuz this is like a chem grade 11 question
caozeyuan
  • caozeyuan
now you know how many moles you have, and how many molar you have
anonymous
  • anonymous
we uusaly do some kind of eqautoon to get the moles right
caozeyuan
  • caozeyuan
can you find the amount of liter
anonymous
  • anonymous
like stoicometry
caozeyuan
  • caozeyuan
it is 1:1 right?
caozeyuan
  • caozeyuan
if you have N mole of H3O+, you need N mole of Oh- to return to neutrality
anonymous
  • anonymous
not sure what u mean
anonymous
  • anonymous
can i do identitys with this
caozeyuan
  • caozeyuan
Well, if you have 10 mole of H3O+, how many moles of OH- do you need to achieve ph=7?
anonymous
  • anonymous
i think i was taught differnetly
caozeyuan
  • caozeyuan
OK, what's your method?
anonymous
  • anonymous
idk identiys?
anonymous
  • anonymous
where u have to seprate all the given info
caozeyuan
  • caozeyuan
Can you figure out how many moles of NaOH you need for neutralization?
anonymous
  • anonymous
i made this eqautioj
anonymous
  • anonymous
hOH+ HN3---> H2O + N3
caozeyuan
  • caozeyuan
It should be NaOH+H3O+=NaN3(aq)+H2O
anonymous
  • anonymous
this is actually whats confusing me
anonymous
  • anonymous
in my notes they are the easist excamples
anonymous
  • anonymous
but when we get question to practice they are much harder
caozeyuan
  • caozeyuan
what exactly do not find hard?
anonymous
  • anonymous
this qestion
caozeyuan
  • caozeyuan
DO you know who to find the correct mole of naOH you need?
anonymous
  • anonymous
wait can i show u my notes?
caozeyuan
  • caozeyuan
sure
anonymous
  • anonymous
1 Attachment
anonymous
  • anonymous
is it similar?
caozeyuan
  • caozeyuan
yep, the same thing happens here
anonymous
  • anonymous
how would u make the enthits ?
anonymous
  • anonymous
wait first
anonymous
  • anonymous
excample 1 has OH and ex 2 has H30 why?
caozeyuan
  • caozeyuan
OH- comes from NaOH
caozeyuan
  • caozeyuan
H3O+ comes from HNO3
anonymous
  • anonymous
ok
anonymous
  • anonymous
wait what ex 2 is it beciuz its acid?
caozeyuan
  • caozeyuan
I didn't understand your question
anonymous
  • anonymous
beacux the question says nitric ACID is it why its H30?
caozeyuan
  • caozeyuan
do you know the difference between strong acid and weak acid?
anonymous
  • anonymous
kinda
caozeyuan
  • caozeyuan
HMO3 is strong acid, so it completely dissociates, HNO3(aq) does not exist. well, it exists as H3O+ and NO3-
anonymous
  • anonymous
okey
anonymous
  • anonymous
damn i need more pratice on these I have test in 2 days
anonymous
  • anonymous
i learn more from here than my teacher :?
caozeyuan
  • caozeyuan
Acid base is really comprehensive, it requires you to apply concepts from different areas like eqalibriu, solution, stoichiometery, etc. So you have to master all these concepts in order to tackle acid base questions easily
anonymous
  • anonymous
:/ whossssssh studying for test is always brutal for me its like i learned nothing
caozeyuan
  • caozeyuan
And I have final in 2 weeks
anonymous
  • anonymous
ur in uni?
caozeyuan
  • caozeyuan
yep, U2
anonymous
  • anonymous
can u help me with this
1 Attachment
caozeyuan
  • caozeyuan
did your professor mention less reactive acid is generated by more reactive ones?
anonymous
  • anonymous
I am in grade 12 :/
caozeyuan
  • caozeyuan
pellet?! almost 3 already?! lets get this down and 'll go sleep
anonymous
  • anonymous
ight
caozeyuan
  • caozeyuan
that would be H3 in my country
caozeyuan
  • caozeyuan
if you react a strong acid with the cb of a weak acid, you get cb of strong acid and weak acid
caozeyuan
  • caozeyuan
the reverse cannot happen i.e. reactant is favored
caozeyuan
  • caozeyuan
If you want to know why, it is because reaction proceeds to form stable product, if product is less stable than reactant, no reaction can happen
anonymous
  • anonymous
okey
caozeyuan
  • caozeyuan
SO from 1 HNO2>HCOOH, from 2 HCOOH > HN3, from 3 HN#>HOBr
caozeyuan
  • caozeyuan
I am here for quite some time so if you have questions, go ahead
anonymous
  • anonymous
@caozeyuan
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anonymous
  • anonymous
I was getting B but the answer is C
caozeyuan
  • caozeyuan
DO you know what second eq point means?
anonymous
  • anonymous
I made the identites H39O4 ,h20, HCO3 , Na
caozeyuan
  • caozeyuan
You used up your H3PO4 in your first eq point, now at second eq point, only H2PO4- exists
caozeyuan
  • caozeyuan
It gives one proton to HCO3-
anonymous
  • anonymous
wait what If u look at my notes the teacher just puts down after choosing the SA and SB ? the teaches changes nothing
caozeyuan
  • caozeyuan
what are SA and SB?
anonymous
  • anonymous
strongest Acid base from the realtice strengs table
caozeyuan
  • caozeyuan
Ok, so what does your note say?
anonymous
  • anonymous
choosse the strongest acid and base and then just make it into equatuoon
caozeyuan
  • caozeyuan
Yes, that is true in most cases, but not this
caozeyuan
  • caozeyuan
The problem here is that multiprotic acid dissociates serially, ie. one at a time
caozeyuan
  • caozeyuan
so at fep, H3PO4 reacts with HCO3-
caozeyuan
  • caozeyuan
then at sep, H2PO4- reacts with HCO3-
anonymous
  • anonymous
wait what
caozeyuan
  • caozeyuan
for example H2SO4 is strong acid right?
anonymous
  • anonymous
yes
caozeyuan
  • caozeyuan
BUT, it actually does not completely dissociates
anonymous
  • anonymous
okey
caozeyuan
  • caozeyuan
This is because it is polyportic
caozeyuan
  • caozeyuan
I.e. it contains more than one proton
caozeyuan
  • caozeyuan
it disscoates step wise
anonymous
  • anonymous
hold on so when they give me a strong acid I have to o this ? but just leave it just the way it is if weak acid?
caozeyuan
  • caozeyuan
only if it is polyportic
caozeyuan
  • caozeyuan
for example, HNO3 is uniprotic strong acid so it completely dissociates in one step
caozeyuan
  • caozeyuan
CH3COOH is weak acid so it is in molecular form in equation
anonymous
  • anonymous
wait so if u look at my notes why did they use NH3 but not NH4 for aqueous ammonia?
caozeyuan
  • caozeyuan
because NH3 is weak base, H2O is weak acid, they do not react
caozeyuan
  • caozeyuan
NH3 is too weak to pull the proton off from Water
caozeyuan
  • caozeyuan
remember I said weak acid cannot form strong acid?
caozeyuan
  • caozeyuan
weak base cannot form strong base too. Because NH3 is weak base OH- cannot be generated by reacting NH3 with water since OH- is strong base
anonymous
  • anonymous
damn I need practice..
caozeyuan
  • caozeyuan
I would suggest you go look at zumdahl's chemistry and chemical reactivity, should have free pdf online, it explains everything clearly

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