buffer solution question A2

for the 2 question in equlibrim, if we had OH- ions eg OH- reacts with H+ and make H20 but this H+ IS being used up so the equilbirum shifts to the right why though? if H+ is being used up the EQ should move to the left where CH3COOH is being broken down to make H+ not to the right where H+ is reacting with CH3COO- to make CH3COOH

(edited 2 years ago)

Reply 1

Hellllpppp

I can’t see the question but shifting to the right means more product made I think you’ve got shifting to the right hand side and left hand side confused

Reply 2

interlanken-fall

Original post by Hellllpppp

I can’t see the question but shifting to the right means more product made I think you’ve got shifting to the right hand side and left hand side confused

let me get a screenshot and explain my question

Reply 3

interlanken-fall

Original post by interlanken-fall

let me get a screenshot and explain my question

here so if we add OH- it reacts with NH4+ and forms NH3 AND H20, so the equilibrium shifts to the left, I understand this as we get more h20 and nh3 it goes to the left which is the reaction where it is broken down creating more NH4+ and OH-.

if we add H+ it reacts with the OH-, however it says the eqilbirum moves to the right to replace the OH- but why though? shouldn't it move to the left as the left is where NH3 and H20 react to form more OH- and NH4+ ions? so why does it move to the right then left

vbhnjmk,.JPG122.1KB

Reply 4

Hellllpppp

Original post by interlanken-fall

if we add H+ it reacts with the OH-, however it says the eqilbirum moves to the right to replace the OH- but why though? shouldn't it move to the left as the left is where NH3 and H20 react to form more OH- and NH4+ ions? so why does it move to the right then left

Moving to the right means NH3 and H20 react to form more OH- and NH4+ ions

When you say shift to right/left it means produce more of whatever is on the side your shifting towards.

Reply 5

interlanken-fall

Original post by Hellllpppp

Moving to the right means NH3 and H20 react to form more OH- and NH4+ ions

When you say shift to right/left it means produce more of whatever is on the side your shifting towards.

I have another question in the screenshot there's a high conc of NH3 as it dissociates weakly, why does it say equilibrium lies way over to the left? should it be on the right as the conc of nh4 and oh are low?

Reply 6

Hellllpppp

Original post by interlanken-fall

If it lies on the left that means there’s more of what’s on the left just like if you shift to the left you produce more of what’s on the left.

Reply 7

interlanken-fall

Original post by Hellllpppp

If it lies on the left that means there’s more of what’s on the left just like if you shift to the left you produce more of what’s on the left.

shouldnt it lie to the right so it can make the conc of nh4 and oh higher? so it can be equal to nh3?

Reply 8

Hellllpppp

Original post by interlanken-fall

shouldnt it lie to the right so it can make the conc of nh4 and oh higher? so it can be equal to nh3?

When the position of equilibrium shifts you do it to oppose a change rather than make each side equal.

“Lie” isn’t talking about shifting the position of equilibrium (le chatliers principal), when at equilibrium the concentration of nh4+ and oh- are just low as the ammonia is a weak base as the lone pair of electrons isnt very available for protonation. This means the Kc value is small.