- WELCOME TO ACID AND BASE CHEMISTRY PART THREE.
THIS VIDEO TUTORIAL WILL FOCUS ON THE CONCEPT
OF THE BRONSTED-LOWRY DEFINITION OF ACIDS AND BASES,
AND THAT CREATES THE CONCEPT OF CONJUGATE ACID-BASE PAIRS.
THESE CONCEPTS ARE REALLY IMPORTANT TO OUR STUDIES,
SO LET'S GET STARTED.
SO, IN A PREVIOUS TUTORIAL,
WE LEARNED ABOUT ARRHENIUS' DEFINITION.
BRONSTED-LOWRY CAME UP WITH A SLIGHTLY DIFFERENT ONE.
THEY AGREED WITH ARRHENIUS THAT AN ACID WAS A PROTON
HYDROGEN ION DONOR, AND SO WE'VE LOOKED AT THOSE FORMS.
WE HAVE OUR INORGANIC ACIDS OR THE ORGANIC ACIDS.
ALL RIGHT. SO, INORGANIC AND ORGANIC, RIGHT?
ORGANIC IS FOR CARBON.
BUT THEN WHERE ARRHENIUS JUST TALKED ABOUT THE ACID,
BRONSTED-LOWRY TALKED ABOUT THE BASE AS WELL.
AND WE SAW THIS IN THE PREVIOUS TUTORIAL THAT THE BASE
WAS A PROTON ACCEPTOR.
AND SO, YOU RECOGNIZE BASES, WE SEE A METAL-
OOPS, THAT'S NOT WANT I WANTED.
WITH HYDROXIDE.
OR WE COULD HAVE AMINES.
OKAY. SO, NOW, LET'S LOOK AT THE IMPLICATIONS
OF THE BRONSTED-LOWRY DEFINITION.
BASICALLY, IT SAYS THAT H+ DOES NOT ACTUALLY EXIST IN WATER.
THAT IF THE PROTON IS DONATED SOME CHEMICAL SPECIES
MUST ACCEPT IT, RIGHT?
SO, LET'S LOOK FOR EXAMPLE AT HYDROCHLORIC ACID
WHEN WE PUT THAT INTO WATER.
IT'S A STRONG ACID, SO WE'LL USE A FULL REACTION ARROW,
THEN WE WOULD SAY THAT THE--THIS IS THE ACID,
SO IT'S THE PROTON DONOR.
AND THEN THE WATER IS GOING TO TAKE THE ROLE OF THE BASE,
AND SO IT'S THE PROTON ACCEPTOR.
AND SO THEN WOULD SHOW THAT WE WOULD HAVE H3O PLUS + CO MINUS.
SO H3O+ IS DESCRIBED AS A HYDRONIUM ION.
AND THEN OF COURSE, WE HAVE THE CHLORIDE.
SO, THE MAIN THING TO KEEP IN MIND HERE IS NOT EVERYBODY
IS GOING TO PAY ATTENTION. AND I DON'T KNOW WHY
I PUT THAT IN CONCENTRATIONS, AND WE'LL GET RID OF THAT,
SO, WHEN WE TALK ABOUT HYDROGEN IONS,
IT'S THE MOST CORRECT THING TO SAY THAT THEY'RE HYDRONIUM IONS,
IN WATER. SO, YOU WANT TO BE AWARE OF THIS,
THOUGH, BECAUSE WHEN YOU'RE READING INFORMATION,
NOT ALL AUTHORS ARE PAYING ATTENTION.
SO, YOU REALLY WANT TO BE ABLE TO INTERCHANGE THESE
WHEN WE ARE IN WATER, THE MOST CORRECT REPRESENTATION
WILL BE H3O+ BUT DON'T BE SURPRISED
IF YOU SEE H+ WRITTEN.
SO, THIS IS WHERE YOU BRING IN YOUR CHEMISTRY UNDERSTANDING
TO FILL IN THE GAPS.
SO, THE SECOND IMPLICATION OF BRONSTED-LOWRY DEFINITION
OF ACID AND BASES IS THIS WHOLE IDEA OF THE PROTON TRANSFER
AND THE--THIS IDEA OF PROTON TRANSFER CREATES THE IDEA
OF CONJUGATE ACID-BASE PAIRS.
SO, CONJUGATE ACID-BASE PAIRS ARE CHEMICAL SPECIES
THAT DIFFER BY ONE PROTON.
ALL RIGHTY. SO, LET'S LOOK AT AN EXAMPLE OF THIS,
WELL, A SIMPLE REACTION, TO ILLUSTRATE THIS CONCEPT.
FOR EXAMPLE, IF WE HAVE THE DIHYDROGEN PHOSPHATE ION
AND IT REACTS WITH WATER. AND THIS IS A WEAK ACID,
SO WE'LL USE EQUILIBRIUM.
SO, THIS--THE DIHYDROGEN PHOSPHATE IS TAKING THE ROLE
OF THE ACID, AND THE WATER IS TAKING THE ROLE OF THE BASE.
AND WE KNOW THAT BECAUSE WHEN YOU LOOK AT THE PRODUCTS,
YOU PROBABLY SHOULD HAVE WRITTEN THAT FIRST,
THERE'S OUR REACTION.
OKAY. SO, HOW DID I KNOW THIS WAS THE ACID?
I KNOW THIS IS THE ACID BECAUSE WHEN I LOOK AT THE PRODUCT,
I SEE THAT IT LOST A PROTON.
SO, WE WOULD DESCRIBE THE DIHYDROGEN PHOSPHATE AS THE ACID
AND THE BIPHOSPHATE AS THE CONJUGATE BASE.
SO, THESE WOULD BE A CONJUGATE ACID BASE PAIR.
ALL OF THESE TERMS, ACIDS AND BASES,
CONJUGATE ACIDS AND BASES, THEY ALL SOUNDS SIMILAR
BUT THEY'RE VERY DIFFERENT.
SO, WHEN WE TALK ABOUT THE ACID AND THE BASE,
WE'RE LOOKING AT THE REACTANTS.
WE SAY THIS IS AN ACID-BASE REACTION BECAUSE WE HAVE
AN ACID REACTING WITH A BASE.
THE DIHYDROGEN PHOSPHATE AND THE BIPHOSPHATE,
THOSE ARE ONE OF THE CONJUGATE ACID-BASE PAIRS.
THE WATER IS SERVING IN THE ROLE OF THE BASE,
SO THEN THE HYDRONIUM ION, RIGHT, THEY DIFFER BY ONE PROTON
SO WE WOULD DESCRIBE THE HYDRONIUM ION
AS THE CONJUGATE ACID OF WATER.
SO, THIS WOULD BE OUR SECOND PAIR OF CONJUGATE ACIDS
AND BASES.
ALL RIGHT. SO, THERE WE RECOGNIZE IT IN A REACTION.
NOW THAT YOU HAVE A CONTEXT FOR THE DEFINITION
OF CONJUGATE ACIDS AND BASES, LET'S SEE HERE.
LET'S WRITE THE CONJUGATE BASE FOR CARBONIC ACID.
SO ANYTIME WE'RE GOING TO WRITE THE CONJUGATE BASE,
WE TAKE AWAY ONE HYDROGEN ION. SO, IF WE HAVE CARBONIC ACID,
THE CONJUGATE BASE WOULD BE BICARBONATE.
IF WE'RE WRITING THE CHEMICAL FORMULA FOR THE CONJUGATE ACID
OF A SUBSTANCE, WE'RE GOING TO ADD ONE HYDROGEN ION.
SO, FOR THIS NIN RIGHT HERE, IT WOULD BECOME H2S,
HYDROSULFURIC ACID.
SO--YEAH, SO THAT FINISHES THAT PAGE.
AND NOW, LET'S HAVE YOU PRACTICE THESE CONCEPTS.
SO, THIS IS PRETTY MUCH THE MAIN POINTS OF THE BRONSTED-LOWRY
DEFINITION AND CONJUGATE ACID-BASE PAIRS.
SO, LET'S--IT TAKE SOME TIME TO PRACTICE THAT
BEFORE YOU GET STARTED ON YOUR HOMEWORK.
ALL RIGHTY. SO, FOR EACH OF THE REACTIONS BELOW,
AND THIS IS A GOOD TIME TO STOP THE VIDEO IF YOU WANT
TO TEST YOUR UNDERSTANDING, AND THEN START IT BACK UP AGAIN.
ALL RIGHT. SO, WE'RE GOING TO LABEL EACH REACTANT
AS AN ACID OR A BASE. AND THEN WE'RE GOING TO LABEL
EACH PRODUCT AS THE CONJUGATE BASE OR THE CONJUGATE ACID,
RECOGNIZING THAT THESE CREATE THE CONJUGATE ACID-BASE PAIRS,
SO, THEN THERE'S THE ARROWS CONNECTING THE TWO.
ALL RIGHTY. SO, WE LOOK AT THE REACTANTS AND THE PRODUCTS
NOTING CHANGE.
SO, HERE WE SEE THE LOST OF A HYDROGEN ION.
SO, THIS IS LOSING HYDROGEN, SO THIS IS THE ACID,
AND THE CONJUGATE BASE.
IF THIS IS TAKING THE ROLE
OF THE ACID, THEN IT MAKES IT VERY STRAIGHTFORWARD.
THE WATER IS TAKING THE ROLE OF THE BASE, AND THEN IT ACCEPTED
THE PROTON TO BECOME THE HYDRONIUM ION,
SO THERE'S OUR CONJUGATE ACID. SO, WE WOULD DESCRIBE THIS
AS AN ACID-BASE REACTION, AND WE'VE IDENTIFIED
THE CONJUGATE ACID-BASE PAIRS.
NEXT EXAMPLE.
SO, LOOK AT THE REACTANTS AND THE PRODUCTS TO LOOK FOR CHANGE.
HERE, WE SEE THE BICARBONATE ION HAS LOST A PROTON
TO BECOME CARBONATE.
SO, AS THE PROTON DONOR WE CALL IT THE ACID.
AND THEN THIS--SINCE THIS DIFFER BY ONE,
THIS WOULD BE OUR CONJUGATE BASE.
SINCE THE BICARBONATE HAS TAKEN THE ROLE OF THE ACID,
THE WATER HAS NO CHOICE OTHER THAN TO BE THE BASE,
THEN WE SEE THIS THE BASE BECAUSE IT'S ACCEPTED A PROTON.
AND SO WE SEE THE CONJUGATE ACID AS HYDRONIUM.
AND SO THIS WOULD BE OUR SECOND CONJUGATE ACID BASE PAIR.
OKAY. ONE LAST EXAMPLE BEFORE YOU GET STARTED
ON YOUR HOMEWORK.
NOW, WE LOOK HERE AND WE SEE, OH, AMMONIA,
IT'S GAINING A PROTON. SO, AMMONIA TOOK THE ROLE
OF THE BASE. IT ACCEPTED THE PROTON
SO THE AMMONIUM ION WOULD BE THE CONJUGATE ACID.
SO, HERE'S ONE PAIR. AND THE WATER, WE SEE THE WATER
ACTED IN A ROLE AS THE ACID THIS TIME.
IT DONATED ONE OF ITS PROTONS TO THE AMMONIUM,
AND SO THE HYDROXIDE IS THE CONJUGATE BASE.
AND SO HERE IS OUR SECOND CONJUGATE ACID-BASE PAIR.
SO, WE HAVE AN ACID-BASE REACTION
AND WE HAVE CONJUGATE ACID-BASE PAIRS.
ALL RIGHTY. SO, THAT CONCLUDES OUR TUTORIAL
ON THE BRONSTED-LOWRY DEFINITION OF ACIDS AND BASES
AND THE IDEA OF CONJUGATE ACID-BASE PAIRS.
PLEASE TAKE A LITTLE TIME RIGHT NOW TO WORK
A FEW HOMEWORK PROBLEMS
TO REINFORCE YOUR UNDERSTANDING.