How Was Chemistry Paper 22, MAY/JUNE 2017?

[HamzaMK_MLG]

in the first part it was "identify" the organic compound so in the boxes we could write structural/displayed or partial displayed formulas. In the next part it was structural formula and only lines were given so structural were a must. And in the last IR part, "names".

Yeah... Really need an A inchemistry tho.. The paper was kind of easy, but that was the problem. I let my guard down

 

[Zaki ali asghar]

The first was ethanoic acid and second methyl methonate in the ir part,what about the bonds in part a of that question? wrote CO and OH for acid and Not sure about ester,what about you guys

 

[Farjad Ilyas]

The first was ethanoic acid and second methyl methonate in the ir part,what about the bonds in part a of that question? wrote CO and OH for acid and Not sure about ester,what about you guys

Same. I wrote CO for ester as well though.

 

[darks]

i wrote C=O of the caboxylic acid. The 2nd part i attempted wrong.

 

[Dukula Jayasinghe]

I wrote structural formula of eyhanoic acid and methyl methanaote instead of.their names will it be acceptable?

They say write the name of the compound, not the formula. Since it was as easier paper, they wont award marks probably.

 

[Dukula Jayasinghe]

What was the answer for how's the percentage decomposition affected by increasing temperature

The percentage decomposition rate will increase. Since the forward reaction is endothermic, increasing the temperature shifts the position of equilibrium to the right hand side producing more yield of the compound(s), so the percentage of HBr decomposed will increase and the percentage of HBr in the mixture will hence decrease.
The question was : Explain what will happen to the percentage composition of HBr in the mixture when the temperature is increased. (3 marks)

 

[Dukula Jayasinghe]

I think these were the points
Increase in temp will shift the equilibirum towards the RHS
Because forward reaction and endo
Hence %of HBr decomposition increase

You must write the percentage composition of HBr will decrease in the mixture. That is what they asked for. I guess you will get 3 marks though.

 

[Dukula Jayasinghe]

So2 + no2 = so3 + no
So3 + h2o = h2so4

The Nitrogen equations was as follows :
NO2 + SO2 --> NO + SO3
SO3 + H2O--> H2SO4
NO + 1/2 O2 --> NO2 (2 marks)

 

[Dukula Jayasinghe]

Nirtrates get leached into rivers. Encourage growth of algae causing an algal bloom. Algae use up oxygen while decomposing dead plants or alvae block the sunlight so plants cant photosynthesize and produce oxygen.

For the total pressure thing I wrote that Kp has no units so its value isnt affected by pressure. I'm not too sure about that one.

You will receive full mark for this.

 

[bettinabelee]

do you have TIPS for chemistry paper 33

 

[darks]

The Nitrogen equations was as follows :
NO2 + SO2 --> NO + SO3
SO3 + H2O--> H2SO4
NO + 1/2 O2 --> NO2 (2 marks)

we had two lines for 2 equations.. i think we could write one of the last 2 equations you wrote, along with the first one.

 

[Hassan (SHT)]

The percentage decomposition rate will increase. Since the forward reaction is endothermic, increasing the temperature shifts the position of equilibrium to the right hand side producing more yield of the compound(s), so the percentage of HBr decomposed will increase and the percentage of HBr in the mixture will hence decrease.
The question was : Explain what will happen to the percentage composition of HBr in the mixture when the temperature is increased. (3 marks)

I Think the question was, what will happen to the percentaage decomposition of HBr as the temperature is increased

 

[Dukula Jayasinghe]

do you have TIPS for chemistry paper 33

Hi, um I got paper 34. The chemistry practical teacher said that paper 33 will be easier than 34, but that comment is not reliable. I guess you might come across organic analysis cos I saw the teacher taking in Felings solution and huge flask of 2,4 DNPH into the room. But this might be for paper 33 or 34. Heating thingy of that MgCO3 etc might come. However, the practical are very different from year 2016 onwards. So it best to go through each one of them before hand..

 

[Dukula Jayasinghe]

we had two lines for 2 equations.. i think we could write one of the last 2 equations you wrote, along with the first one.

Yeah. The question was effectively not clear. They asked the equations for the catalytic conversions of NO2 in formation of acid rain. So I wrote both. BTW, I guess yeah, you will receive 2 marks.

 

[Dukula Jayasinghe]

y

I Think the question was, what will happen to the percentaage decomposition of HBr as the temperature is increased

Yeah, same thing.

 

[anastasia grey113]

Yeah. The question was effectively not clear. They asked the equations for the catalytic conversions of NO2 in formation of acid rain. So I wrote both. BTW, I guess yeah, you will receive 2 marks.

they asked for the role of NO2 in the formation of acid rain
It is an oxidising agent
n there were two equations leading to formation of H2SO4 i.e. acid

 

[Hassan (SHT)]

they asked for the role of NO2 in the formation of acid rain
It is an oxidising agent
n there were two equations leading to formation of H2SO4 i.e. acid

They did asked for the role, but i Think the Word CATALYTIC is the most important term and this is what the examiner is seeking for, i asked my teacher and he said we have to write Catalytic oxidation, i think writing only oxidation is wrong.

 

[anastasia grey113]

They did asked for the role, but i Think the Word CATALYTIC is the most important term and this is what the examiner is seeking for, i asked my teacher and he said we have to write Catalytic oxidation, i think writing only oxidation is wrong.

was the word catalytic used?
becuz NO is a catalyst...not NO2

 

[Hassan (SHT)]

Well this is what written in coursebook
Read the last line of this image

 

[anastasia grey113]

Well this is what written in coursebook
Read the last line of this image

View attachment 62192

shiz :/
so what is this catalyst or oxidising agent or both?