Chemistry: Post your doubts here!

[TheStallion-Reborn]

Can someone please explain the ideal gas equation? It is making no sense to me.

 

[sitooon]

Whats a smooth curve ?

 

[Thought blocker]

Whats a smooth curve ?

It means draw curve at once, no sharp edges at curve, no repetition

 

[sitooon]

It means draw curve at once, no sharp edges at curve, no repetition

What you mean by no repetition ?
do we join points by scale ?

 

[Thought blocker]

I mean no repeats on line (No scribbling on one line) No, it should be free hand drawing...

What you mean by no repetition ?
do we join points by scale ?

 

[sitooon]

In on2006 paper 4
can some one tell me why they chose ph to be the pka ?

 

[Thought blocker]

In on2006 paper 4
can some one tell me why they chose ph to be the pka ?

Still As level kid here.

 

[sitooon]

Still As level kid here.

But i didnt ask u

 

[Thought blocker]

But i didnt ask u

someone, includes me

 

[Faaiz Haque]

well about how should we know this, they are all general equations and you sort of have to remember them!
with phosphorus and iodine, there will be replacement of OH by I
with conc. H2SO4, there will be elimination of water, for that we will take the -OH group from one carbon and the -H from the carbon right next to it, and it will form an alkene
with hot K2Cr2O7, the double bond will dissolve (if any) and the -OH will be oxidised to -COOH, but not in tertiary alcohols!, they wont react!

For the phosphorus iodine, does iodine always replace OH in a reaction, or just for that alcohol the one that they gave?
And for h2SO4, does it always eliminate water?

Ty for help man, its hard to memorize when I dont understand

 

[Abdel Moniem]

http://papers.xtremepapers.com/CIE/... AS Level/Chemistry (9701)/9701_w10_qp_22.pdf
Question 1 Ciii , iv) and d)

 

[Haris Bin Zahid]

Which pair of reactions could have the same common intermediate?

W CH3CH2CH3 → intermediate → (CH3)2CHCN
X CH3CH(OH)CH3 → intermediate → (CH3)2C(OH)CN
Y CH3CH=CH2 → intermediate → CH3CH(OH)CH3
Z CH3CO2CH2CH2CH3 → intermediate → CH3CH2CH2Br

A W and X
B W and Y
C X and Z
D Y and Z

The answer is B. Explanation?

 

[ZaqZainab]

http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Chemistry (9701)/9701_w10_qp_22.pdf
Question 1 Ciii , iv) and d)

c(iii) th gas in (ii) is CO2 and if you see total of gas formed is 40 but only 30 remains when the tottal gas is shaken with KOH(aq) se where did the 10 go it reacted with Koh(aq) and the gas is CO2 so 10cm^3
iv) they gave 50 O2 whcih gave us total of 40 cm^3 of gases of which 10 is CO2 so we have 30 left This 30 is O2 which is left from 50 so 50-30=20cm^3 got it?
d) the ms explains it quite well though but here we will use the volume ratio from balancing in b the ration between A used is 10 and CO2 produced is 10 so 1 cm^3 of A give 1 cm^3 of Co2 x=1
and 10 cm^3 of A reacts with 20 cm^3 of O2 so 1cm^3 of A reacts 2 cm^3 of O2
x=1
2=x+(y/4)
2=1+(y/4)
y=4
CxHy will be CH4

 

[Snowysangel]

To convert an alcohol into oliec acid (an acid with a double bond), why do you add dilute hcl?

 

[TheStallion-Reborn]

Can someone please help me with bond angles? AB2/AB3 systems etc I've got absolutely no clue what it is. asma tareen

 

[asma tareen]

For shape of the molecules and the angles the first thing that u need to look for is the number of electron pairs

there are two types of electron pairs : bond pairs n lone pairs
and all the single bond double bonds and triple bonds are considered as bond pairs
if we take an example of AB2 molecule, like BeF2, we will first look for the number of bond pairs n lone pairs
Be contains 2 electrons so it will form 1 bond pair with each fluorine so the structure will be like
F - Be - F now if u observe both fluorines are opposite that means there is 180° angle between them due to maximum repulsion of electrons now we can say the shape is linear :/ I hope u get it

Can someone please help me with bond angles? AB2/AB3 systems etc I've got absolutely no clue what it is. asma tareen

 

[DeViL gURl B)]

Can I please get the summary of organic chemistry..for AS in an easy form? Thank you

 

[sitooon]

paper5 :
how you would measure the independent variable ( concentration of HCl )
markscheme says : "Dilutes a range of volumes of HCl" how ?

 

[asma tareen]

paper5 :
how you would measure the independent variable ( concentration of HCl )
markscheme says : "Dilutes a range of volumes of HCl" how ?

By adding water ._.

 

[Thought blocker]

By adding water ._.

I could too say that.