OCR Gateway Chemistry C4C5C6 - 13/06/13

Scroll to see replies

Can anyone explain how an ion-exchange resin works?

yeah okay so basically it has sodium ions on its surface and when calcium ions from hard water flow past they are attracted to the surface and stick to it, knocking the sodium ions into the water. The water is soft because the calcium ions have been removed and the sodium ions do not effect the soap. The calcium ions can then be removed by concentrated salt solution as it knocks them off and replaces them with fresh sodium ions.

sorry if that made no sense xx

Reply 401

Daniel97g

Original post by Knowing

You're welcome ^^

(If all the sodium ions have been replaced, you just flush the column with NaCl solution again, clearing away the Ca/Mg ions, and regenerating it with new sodium ions)

Understood, how do you what atoms are more reactive? (for example, in this case Mg and Ca are more so than Na?) Thank you!

Reply 402

Knowing

Original post by Daniel97g

Understood, how do you what atoms are more reactive? (for example, in this case Mg and Ca are more so than Na?) Thank you!

Mg and Ca are both ions with a charge of +2. This is double the charge of Na, which has a charge of +1, so Mg/Ca attract twice as much as Na.

Reply 403

Daniel97g

Original post by Knowing

Mg and Ca are both ions with a charge of +2. This is double the charge of Na, which has a charge of +1, so Mg/Ca attract twice as much as Na.

Oh right, compare fermentation and hydration for producing ethanol?

Reply 404

Puffin111

What are the total UMS marks that the whole gcse is out of? And how many would you need total for a A* and an A? Thanks!

Reply 405

Mutleybm1996

Original post by Knowing

You're welcome ^^

Basically you have an "ion-exchange column", which is packed with small beads. When you flush sodium chloride solution through it (salt water basically), the sodium ions get attached to the ion-exchange resin/beads. When hard water (water with calcium and magnesium ions in) passes through the ion-exchange column, the calcium/magnesium ions in the water are swapped with the sodium ions in the column, because calcium is more attractive. Therefore, the sodium ions replace the calcium/magnesium ions in the hard water, softening it.

(If all the sodium ions have been replaced, you just flush the column with NaCl solution again, clearing away the Ca/Mg ions, and regenerating it with new sodium ions)

Original post by ChloBrown98

Ions can be formed when electorns are lost or gained if this helps :smile:

and I have no clue about what the 'resin' part is. Sorry :frown:

Original post by izzzyyay

You guys have cleared c4/5/6 up for me! Thanks :smile:

I'm unprepared -.-

Posted from TSR Mobile

(edited 10 years ago)

Reply 406

AR-13

Any one prepared any 6mark answers for c4c5andc6?

Posted from TSR Mobile

Reply 407

Knowing

Original post by Daniel97g

Oh right, compare fermentation and hydration for producing ethanol?

Fermentation:

Renewable;
Low temperature, medium pressure;
Low percentage yield;
Low atom economy;
Batch process.

Hydration:

Non-renewable (ethene from crude oil);
High temperature + pressure;
High percentage yield;
High atom economy;
Continuous process.

Reply 408

AR-13

Original post by Knowing

So hydration wud be better right? :lolwut:

Posted from TSR Mobile

Reply 409

Knowing

Original post by AR-13

So hydration wud be better right? :lolwut:

Posted from TSR Mobile

That's for you to choose :tongue:

If there's a 6 marker on it, it'll probably ask you which you think is better and why, so just list the differences and use your own judgement - you can say either could be better if you justify it.

Reply 410

BP_Tranquility

Original post by Knowing

I think fermentation has a high yield and low atom economy whilst hydration has a low yield and high atom economy. The hydration reaction is reversible which causes the low yield whilst fermentation is not reversible, which results in it having a higher yield...
This is what my revision guide is telling me :redface:

Posted from TSR Mobile

(edited 10 years ago)

Reply 411

Puffin111

Really hoping most people are unprepared as it is one of the later exams so that the grade boundaries will be lower... :frown:

Reply 412

DeadUnicorn

Original post by Puffin111

Really hoping most people are unprepared as it is one of the later exams so that the grade boundaries will be lower... :frown:

Let's hope so, I am literally just cramming everything from all the units, starting C6 now. :eek:

Reply 413

Knowing

Original post by BP_Tranquility

Posted from TSR Mobile

If it's worked, I've attached what my textbook says.

Snapshot_20130612.JPG55.9KB

Reply 414

Knowing

It would make sense that a reversible reaction would be 100% yield, since the unreacted reactants can be re-used again.

Also, you would lose a lot of yield during fermentation, as you have to evaporate and filter and what not to remove the ethanol from the yeast.

(edited 10 years ago)

Reply 415

BP_Tranquility

Original post by Knowing

True, but surely a reversible reaction also allows an equilibrium to be formed? Because hydration requires a large amount of energy which would increase the chances of the backward reaction speeding up, breaking down the product and reducing yield... :smile:

Posted from TSR Mobile