VCE Chemistry Question Thread

[jyce]

oooh that would make much more sense - but isn't there CO2 in the atmosphere as well?

CO₂(g) would be more concentrated inside the drink.

[blacksanta62]

Can anyone explain to me how pH affects enzyme activity from a chemistry pov. My chem teacher said that explanations given in biology would not be sufficient at times. He did explain it to be but it doesn't seem to be sticking/being clear as day. Thank you

[Swagadaktal]

Can anyone explain to me how pH affects enzyme activity from a chemistry pov. My chem teacher said that explanations given in biology would not be sufficient at times. He did explain it to be but it doesn't seem to be sticking/being clear as day. Thank you

So enzymes work within an optimum pH range and wane in effectiveness when the pH is increased or decreased. They work on a) dipole-dipole bonds with the substrate and ion-dipole bonds (are there any more? I feel like there's one more) - so by changing the pH it changes the charge of the enzyme, which would change the ion-dipole bonds and dipole-dipole bonds - thus effecting the efficiency of the enzymes coz it cant make those bonds anymore ya feel?

(kind of rusty here we did this chapter ageeeeeeeeees ago) - someone hmu if my wording/theory is wrong

[jyce]

So enzymes work within an optimum pH range and wane in effectiveness when the pH is increased or decreased. They work on a) dipole-dipole bonds with the substrate and ion-dipole bonds (are there any more? I feel like there's one more) - so by changing the pH it changes the charge of the enzyme, which would change the ion-dipole bonds and dipole-dipole bonds - thus effecting the efficiency of the enzymes coz it cant make those bonds anymore ya feel?

(kind of rusty here we did this chapter ageeeeeeeeees ago) - someone hmu if my wording/theory is wrong

Changing the pH doesn't change the dipole-dipole bonds; it only changes the ionic interactions.

[grannysmith]

So enzymes work within an optimum pH range and wane in effectiveness when the pH is increased or decreased. They work on a) dipole-dipole bonds with the substrate and ion-dipole bonds (are there any more? I feel like there's one more) - so by changing the pH it changes the charge of the enzyme, which would change the ion-dipole bonds and dipole-dipole bonds - thus effecting the efficiency of the enzymes coz it cant make those bonds anymore ya feel?

(kind of rusty here we did this chapter ageeeeeeeeees ago) - someone hmu if my wording/theory is wrong

Also remember that the enzyme's tertiary structure can be affected (since it can involve ionic interactions), inducing slight but significant conformation changes which ultimately leads to decreased catalytic activity.

[zsteve]

The reason pH changes the tertiary structure is because of ionic interactions arising (for example) from protonation of -NH2 groups to -NH3+, and deprotonation of -COOH to COO- groups. (In case of low and high pH respectively)

[Swagadaktal]

ooh that's a critical distinction, thanks guys

[blacksanta62]

Shoot! Those are some very helpful posts. I'm in school rn so I just skimmed over them but it'l make more sense when I read it carefully. Thanks guys 

[Jakeybaby]

In my latest Chemical Practical Report, the relationship between the concentration of the electrolytes and the voltage produced was discovered, as the concentration increases, so does the voltage. However, a question that is incorporated into the report is in regards to the future predictions that could be made. Would the voltage eventually plateau? What would happen in regards to future events with the galvanic cell with Cu & Mg?

Sorry, does anyone know the answer to this question?

[Apink!]

Hello,

Could someone please help me answer this question?
What's the difference between rate of reaction and yield of reaction and how can you tell if a changing environment of the reaction system (like increasing temp, decreasing pressure etc) will affect the rate of reaction or the yield of reaction

I really appreciate your help!

[Swagadaktal]

Hello,

Could someone please help me answer this question?
What's the difference between rate of reaction and yield of reaction and how can you tell if a changing environment of the reaction system (like increasing temp, decreasing pressure etc) will affect the rate of reaction or the yield of reaction

I really appreciate your help!

Um so for pressure/dilution, if there number of products and reactants are the same (molar amounts), then altering the pressure or concentration of a solution would not have an impact on the yield of reactants and products (it would remain the same), however, increasing pressure and concentration would increase the rate of reaction (collision theory).
For temperature, i think it always changes the yield because all reactions are endothermic or exothermic, but tbh not too sure about that point.
And for rate of reaction only, a catalyst will only increase the rate of reaction and would not alter the yield.

hope this helps

[blacksanta62]

Is that all unit 4 stuff? I've heard of some of the things you said (e.g. collision theory) but I just can't recall any of the other stuff 

[Swagadaktal]

Is that all unit 4 stuff? I've heard of some of the things you said (e.g. collision theory) but I just can't recall any of the other stuff 

yea all unit 4

[The Usual Student]

Um so for pressure/dilution, if there number of products and reactants are the same (molar amounts), then altering the pressure or concentration of a solution would not have an impact on the yield of reactants and products (it would remain the same), however, increasing pressure and concentration would increase the rate of reaction (collision theory).
For temperature, i think it always changes the yield because all reactions are endothermic or exothermic, but tbh not too sure about that point.
And for rate of reaction only, a catalyst will only increase the rate of reaction and would not alter the yield.

hope this helps

just adding on to that,
Diluting can lead to a decrease in the amount of particles capable of reacting, if the substance being diluted is the limiting reagent, then it would lead to a decrease in the yield of the reaction as less particles are present and capable to react/collide. So make sure you check the molar ratios and amounts of the reagents present before you make any decisions and decide what is DRIVING the reaction.

[blacksanta62]

Sorry, does anyone know the answer to this question?

Sorry, haven't covered galvanic cells yet. Hopefully a bump wil result in your question being seen