OCR Salters Chemistry F335 12th June 2013 Exam revision thread

Original post by chemistryfailure

What did everyone put for trans having higher bp?

Trans chains are straighter and more regular so they can line up and pack together more closely. This means intermolecular bonds are stronger and more numerous because there are more points of contact so more idid bonds form and the chains require more energy to separate.

Reply 722

Original post by Futuristicmedic

For the insecticide did anyone put about it going into drinking water and affecting humans

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i didn't think bout the drinking water, i said it accumulates along the food chain and human eat the other mammals so could be a healthy hazard/toxic ( this was in story lines too about DDT not just my biology knowledge speaking)

Reply 723

Original post by Callumhamby

Is it me or was there a lot more equilibrium and acid equilibrium questions than normal?

It felt like that to me too.

I didn't realise F335 was a maths paper :s-smilie:

Reply 724

millz186

does anyone remember the answers for the pH calculations?

Reply 725

Mattywooda

Fairly sure it was oxidation? Losing a hydrogen is that...

Reply 726

EdwinLo

Original post by C.JTop

i didn't think bout the drinking water, i said it accumulates along the food chain and human eat the other mammals so could be a healthy hazard/toxic ( this was in story lines too about DDT not just my biology knowledge speaking)

Humans are mammals too so surely it is toxic to humans just to inhale?

Reply 727

Mattywooda

prove Ka = 1.7E-4, when pH is 3.77.

Then pH when HA = A-, 3.77.

pH when half acid has reacted with NaOH, pH = 4.07

Reply 728

suncake

14

Original post by Mattywooda

Fairly sure it was oxidation? Losing a hydrogen is that...

Agghh. I wrote that first, then changed it :facepalm:

Got the same pH values as you for the buffers. :smile:

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Reply 729

Original post by Reina

Trans chains are straighter and more regular so they can line up and pack together more closely. This means intermolecular bonds are stronger and more numerous because there are more points of contact so more idid bonds form and the chains require more energy to separate.

I put they way more points of contact, they was less distance between some parts of the chains unlike in cis were the chains where straighter but prevented from packing closely by the ester bond. This means the intemolecular forces ( instantenuos induced dipole interctions) are strong in trans oil so more energy need to separate out the chains inorder to boil the liquid.

Reply 730

Mattywooda

Original post by EdwinLo

Humans are mammals too so surely it is toxic to humans just to inhale?

Yeah.

"Damn. I wrote the complete opposite. I said the shell gets stronger."

It's in storylines :smile:

Reply 731

autodidactmedic

what did everyone put for the transition metal & coloured complex 5 or 6 marker ?

Spoiler

Reply 732

Original post by millz186

does anyone remember the answers for the pH calculations?

I got 3 point something for the one that was followed by the "which assumption makes the calculation less accurate" question (or something along those lines).

Reply 733

chemistryfailure

I put 2HCOOH + CaCO3 = CO2 + H2O + CA(OH)2 ...... is that wrong?

Reply 734

Reyoru

1

Original post by Mattywooda

Fairly sure it was oxidation? Losing a hydrogen is that...

It lost a proton so there was no change in electrons.

Reply 735

Original post by EdwinLo

Humans are mammals too so surely it is toxic to humans just to inhale?

inhaling? perhaps but i was thinking that humans would eat the insecticide at higher concentration that were more toxic

Reply 736

autodidactmedic

Original post by C.JTop

I put they way more points of contact, they was less distance between some parts of the chains unlike in cis were the chains where straighter but prevented from packing closely by the ester bond. This means the intemolecular forces ( instantenuos induced dipole interctions) are strong in trans oil so more energy need to separate out the chains inorder to boil the liquid.

Ditto. Do you think if I stated pd-pd as an interaction between the hydrocarbon chains that I'll lose a mark?

Reply 737

Original post by AmirHabeeb

It lost a proton so there was no change in electrons.

yeah the Nitrogen was N- , so i put reduction?

Reply 738

Reyoru

1

Original post by C.JTop

yeah the Nitrogen was N- , so i put reduction?

Oxidation/Reduction involve a change in number of electrons. There was no change. I think it's elimination. :colondollar:

Reply 739