Chemistry: Post your doubts here!

[gary221]

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

remember d formula, Kc = Molar conc of product/ molar conc of reactants (both raised to the power of thr stoichiometric coefficient)
Initial conc of H2 n I2 is 0.2 n 0.15 resp. Inititl conc of HI = 0
Final conc of HI = (0.26/2) as thr r 2 moles of HI formed
So. final conc of H2 = 0.20-0.13 =0.07
Final conc of I2 = 0.15 - 0.13 = 0.02

 

[gary221]

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

hey does sum1 know how 2 solv this??

 

[hmlahori]

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?​

​

 

[hm12]

hey does sum1 know how 2 solv this??

2 bond pairs 0 lone pairs 180 degree shape is linear
3 bond pairs 0 lone pairs 120 degree shape is trigonal planor
4 bond pairs 0 lone pairs 109.5 degree shape is tetrahedral
3 bond pairs 1 lone pairs 107 shape is trigonal pyramedal
2 bond pairs 2 lone pairs 104 bent shaped
5 bond pairs 0 lone pairs 90,120 degree shape is trigonal bipyramedal
6 bond pairs 0 lone pairs 90 degree shape is octahedral


Follow this and the answer will be C sulphur has two bond pairs two lone pairs so x would be 104 degree carbon has 4 b0nd pairs and 0 lone pairs so y is 109.5 degree nitrogen has 3 bond pairs and one lone pair so z is 107 degree so y>z>x so C is the answer

 

[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