Quick Revision - Buffer solution calculations

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Күн бұрын

Walkthroughs of four different buffer solution past exam questions. Each one tests a different aspect of the topic.
A real test of your buffer solution understanding!

Пікірлер: 57

@matildawillcox1693 5 жыл бұрын

Love that you include past questions! I tend to use Henderson-Hasselbalch but I think Kaacidoversalt has swayed me ahaha

@MaChemGuy 5 жыл бұрын

Matilda Willcox Haha indeed! Kaacidoversalt is the way forward. Good luck tomorrow 👍

@matildawillcox1693 5 жыл бұрын

@@MaChemGuy Thank you! I had a bit of a meltdown earlier and decided to watch all your vids and they've helped calm me down a bit x

@MaChemGuy 5 жыл бұрын

Matilda Willcox That’ll be my monotonous voice (as someone said I had today) Good that you’re all calm now, try and stay that way

@DB-us6sb 5 жыл бұрын

How comes you added 0.5 moles to the final products? I thought that on addition of H+ ions the equilibrium shifted to the left

@ammarafahad8094 2 жыл бұрын

Hi Sir, at 2:28 could u plz explain again why the buffer moves to the right and why does the acid conc goes down and salt conc goes up?

@malanhemal6574 2 жыл бұрын

at 3:48 sir, do you need to know the molar ratio from before, for Mg reaction with H+ that 2H+ reacts with Mg, inorder to do the question?

@tenfootman7600 Жыл бұрын

Machemguy @ 3:35 let's say an acid was added instead of Mg would the acid final moles be 1.5 and the salt final moles be the same so 1 ?

@mjian815 5 жыл бұрын

at 8:22 can we use the concentrations as 2.04 moldm-3 acid and 1.00 moldm-3 salt as this is the exact ratio given from the calculation?

@MaChemGuy 5 жыл бұрын

Michael Jian That would be fine

@teclar4457 Жыл бұрын

Can we use ka + log acid ÷salt

@firminobecker7400 5 жыл бұрын

Such a Time saver thankyou

@MaChemGuy 5 жыл бұрын

Firmino Becker Glad you approve!

@firminobecker7400 5 жыл бұрын

MaChemGuy would it be possible to make quick revision videos on as organic chem , like haloalkanes

@MaChemGuy 5 жыл бұрын

Firmino Becker Good shout. Will add to the list

@MaChemGuy 5 жыл бұрын

Firmino Becker Done!

@firminobecker7400 5 жыл бұрын

MaChemGuy just checked it out thank-you so much , my only issue now is trying to retain the entire spec and being equally good at AS as A2 🙁

@mashalajan7419 2 жыл бұрын

for the last question, I used HA=H+squared/ka to get a value for the weak acid and then rearranged the kaacidoversalt to get concentration of salt. I got 0.000576moldm3 for acid and 0.000282moldm3 for salt which is pretty much the 2.04/1 ratio of acid/salt. would this get me any marks??

@MaChemGuy 2 жыл бұрын

Yup

@nosaii4660 2 ай бұрын

at 3:15 why are the final moles 0.5 for HA and 1.5 for A- if 0.5 moles of H+ is removed?

@chelsea9575 5 жыл бұрын

How do you know the magnesium ions are going to react with the H+ ions?

@MaChemGuy 5 жыл бұрын

Chelsea Learned in Y12 acid + metal = salt + hydrogen and that it’s the H+ ion they react with

@faizahbegum5257 4 жыл бұрын

MaChemGuy what if they said a non metal?

@mashaaln8764 3 жыл бұрын

@@MaChemGuy Hi, BIG fan here. I'm confused, I'm pretty sure the Mg doesn't react with H+ ions (since Mg isn't negatively charged) Question 1 Part 2 Correct me if I'm wrong, but I think its the C2H5COOH reacting with the Mg that makes (C2H5COO)2Mg and that then FULLY dissociates into 2C2H5COO- and Mg+ (because aq) so hence you get a reduction of 0.5 mol of C2H5COOH but an increase of 0.5 mol of C2H5COO- ---- p.s I came to this conclusion from watching your other vids.

@chlorine392 Жыл бұрын

in min 3:46 you put salt over acid cux acid is 1.5 not 0.5 the salt in 0.5 or am i wrong

@alexiaplacinta5468 2 жыл бұрын

How do you know magnesium will react with hydrogen at 2:18 ?

@scrumdum1 Жыл бұрын

It is because group 2 elements react with acids to produce salts and hydrogen gas, they donate the outer 2 electrons to the hydrogen ions in the acid so form Mg2+ + H2 So I think it doesn't react with the H+ ions in the right side of the buffer equation but the hydrogen in the actual acid in the left. Then you'll get 2C2H5COOH + Mg > (C2H5COO)2Mg + H2, which shows why the moles of acid drops by 0.5 and the moles of C2H5COO- increases by 0.5

@nisargapoudel3911 3 ай бұрын

what if it reacted with the propanoic acid ? @@scrumdum1

@user-mg8yq7dg3w 9 ай бұрын

Awesome

@user-mg8yq7dg3w 9 ай бұрын

Thx

@CandyFace2000 5 жыл бұрын

Could you have also rearranged it to get Ka/[H+]= [salt]/[acid] because when I tried it I did that and got 0.49moldm13 of salt over 1moldm-3 acid which is pretty much the same ratio? Thank you.

@MaChemGuy 5 жыл бұрын

That's fine, just be careful you get the ratio the right way round when giving your answer. The way I rearranged gives the ratio [Acid]/[Salt] ratio directly (as asked in the Q) whereas your way gives it the other way round. Hope that helps

@babs8958 Жыл бұрын

why would it react with H+ not anything else

@oswin4715 5 жыл бұрын

Where does the 0.5 come from at 3:06?

@MaChemGuy 5 жыл бұрын

Oswin Mole ratio between Mg and H+

@oswin4715 5 жыл бұрын

@@MaChemGuy ahh thank you

@annabelb4266 5 жыл бұрын

at 8:18 why does the acid have to have twice the concentration of the salt

@MaChemGuy 5 жыл бұрын

Annabel B Because the ratio came out as 2:1

@isabelokeke6255 5 жыл бұрын

@@MaChemGuy but the equation is a 1:1 ratio

@darkredsrevenge6154 5 жыл бұрын

@@isabelokeke6255 Acid/Salt = 10^-3.55/10^-3.86. Look at the numbers from the inverse log on your calculator. Acid conc is around double the conc of the salt from this, which is why the value came out as 2.04