Chemistry: Post your doubts here!

[USMAN Sheikh]

Can someone please give explanations to these paper 1 questions?​

http://www.xtremepapers.com/papers/...d AS Level/Chemistry (9701)/9701_w08_qp_1.pdf​

Q3 What does 'ground state' mean? And r we supposed to write the '1s2 2s2....' electronic configuration to know the answer?​

Q21 Does an alcohol get oxidised by hot, concentrated manganate(7) ions?​

Q31 Why is the answer B not A? all the three statements seem correct.​

and Q38 Why cant the answer be B?​

Ground state mean normal electronic configuration on hybridization yes u need to write it
yes alcohol get oxidised and form diol
NO there must be flourine atom aswell in fire extinguiosher

 

[amatyasrizan]

How do i guess the products of thermal decomposition?
Q.MgNo3 (when heated) = Mgo+No2+O2.
I think it doesn't satisfy the LHS.Please explain me the answer..

 

[JD REBORN]

http://www.xtremepapers.com/CIE/International A And AS Level/9701 - Chemistry/9701_s10_qp_12.pdf
Q12,15,21,33,40

 

[gary221]

How do i guess the products of thermal decomposition?
Q.MgNo3 (when heated) = Mgo+No2+O2.
I think it doesn't satisfy the LHS.Please explain me the answer..

whn grp 2 nitrates r heated they form a metal oxide, nitrogen dioxide n oxygen...tht is fixed for all grp 2 metals...then u hv 2 balance d equation..
ie 2 Mg(NO3)2 = 2 MgO + 4 NO2 + O2
try this :http://www.chemguide.co.uk/inorganic/group2/thermstab.html
hope i helped...

 

[gary221]

http://www.xtremepapers.com/CIE/International A And AS Level/9701 - Chemistry/9701_s10_qp_12.pdf
Q12,15,21,33,40

For 12, the ans is A, bcoz whn u acidify the pool, the OH ions will react wth the H ions in the acid to neutralise it...this will result in a decrease in the conc of OH ions, n following Le Chatliers principle, d equilibrium will shift 2 d products side, more products ie HOCl will b fromd...
Hope i helped...

 

[gary221]

for 15, d ans is A, bcoz, the 1st test proves tht u hv a halide which is nt fluoride since u gt a ppt.
the 2nd test is to define which halide is present, since the ppt dissolves in excess NH3, this shows that d halide present is Chloride...n since A is the only option with chloride the ans is A...

 

[gary221]

for 21, the ans is B, bcoz, since the 2 alcohols r primary, they will both react with potassium manganate ie get oxidised, this rules out A..
since both the alcohols have only 1 OH grp, the OH grp will get replaced by Na & Cl, thus substitution reaction same for both alcohols, this rules out C n D
So d only option remainng is B, bcoz both d alcohols hv differnt positioning of C atoms...so d ans is B

 

[gary221]

For 33, the ans is D ie 1 only is correct. It is simply calculating the oxidation no. of the elements participating in the reaction ie undergoing any change. If thr is an increase n decrase of oxidation no., its a redox reaction...​

Hope i helped...​

 

[DPratik]

thank you sooooooooooooo much bro..

dude do u have any good chemistry note ( organic notes)..if you do please tell me about them and thank u again!

i mostly refer to www.chemguide.co.uk and some other books !!!

 

[DPratik]

Hey can sum1 explain why the ans for this is c
View attachment 7369

first see that there are no lone pair in C-C bond which means it has the largest angle,then see that there is 2 lone pair in S due to which C-S bond is the most smallest....the reason for all these because lone pair-lone pair repulsion is too much which means the bond angle decreases to a larger amount !!

 

[DPratik]

Thankyou for the previous response Hm12 and histephenson007!Here goes another one..Why isnt the answer C?View attachment 7371

I think the answer must be B because if you increase the temperature then the kinetic energy increases which means the velocity increases,so if the velocity increases then the rate of collision increases and if the rate of collision increases then the molecules get enough energy to proceed the reaction in a faster rate !!

 

[UltimateHustla]

hey guys i heard we gona get screwed in paper 33 and 34

 

[iKhaled]

hey guys i heard we gona get screwed in paper 33 and 34

who doesn't get screwed in a practical paper? lol

 

[smzimran]

who doesn't get screwed in a practical paper? lol

Thats not true if you do it well, you will be fine
I wasnt screwed, got a good grade

 

[iKhaled]

Thats not true if you do it well, you will be fine
I wasnt screwed, got a good grade

did u practice a lot in skl? and what was ur grade in it?

 

[shan5674]

http://www.xtremepapers.com/papers/CIE/Cambridge International A and AS Level/Chemistry (9701)/9701_s10_qp_11.pdf

Q-14,22,25,30, 35 can someone please explain

 

[smzimran]

did u practice a lot in skl? and what was ur grade in it?

No, did around 8-9 in total throughout the year! LOL

 

[mehdi1028]

Can someone provde me wth the organc chemstry notes?? AS Level?

 

[DPratik]

http://www.xtremepapers.com/papers/CIE/Cambridge International A and AS Level/Chemistry (9701)/9701_s10_qp_11.pdf

Q-14,22,25,30, 35 can someone please explain

for question 14) the answer is sodium cholride because there is one thing which you must look for to distinguish,chloride ion reacts with an excess of dil NH3,bromine ion reatcs with conc NH3 and Iodine ion doesn't react,so as the question has said the compound X reacts with dil NH3 which means the answer is sodium chloride !!!
for question 22) you can see check one by one,both the alcohols react the same way with KMnO4,both the alcohols react the same with Phosphorous Penatcholride and both react the same way with sodium but in the case of sulphuric acid,the longer alcohol chain may get oxidized where as the shorter chain won't get oxidized !!
for question 30) draw the displayed formulae and see that you can find both chiral center and cis-trans isomerism in D,you may find chiral center in B also but there is not cis-trans isomerism!!
for question 35) its obvious that in car engine carbon won't be form so that it will react in that way instead CO would be formed so the answer is nitrogen and sulphur !!

 

[DPratik]

The ans in C.How come the denominator is (0.07*0.02) ? Please explain..
View attachment 7373

as 1 mole of iodine and 1 mole of hydrogen forms two mole of mole of hydrogen Iodide.So at equilbrium when 0.26 mole of hydrogen iodide is formed which means 0.13 mole of iodine and 0.13 mole of hydrogen was used up so at equilbrium you got (0.15-0.13) mole of hydrogen and (0.15-0.13) mole of iodine left !!