Chemistry: Post your doubts here!

[nirajsuroopjet]

hi you all, am searching for chemistry p4 topical past papers for chemistry of live, applications of analytical chemistry and design and material

 

[Jinosupreme]

What will react differently with the two isomeric pentanols, (CH3)3CCH2OH and (CH3)2CHCH2CH2OH?
A acidified aqueous potassium manganate(VII)
B concentrated sulphuric acid
C phosphorus pentachloride
D sodium

Why is it B? Both are primary alcohol, should it both become Alkene?

 

[KZW]

What will react differently with the two isomeric pentanols, (CH3)3CCH2OH and (CH3)2CHCH2CH2OH?
A acidified aqueous potassium manganate(VII)
B concentrated sulphuric acid
C phosphorus pentachloride
D sodium

Why is it B? Both are primary alcohol, should it both become Alkene?

(CH3)3CCH2OH will not dehydrate into an alkene. The reason being is that there can't be a double bond formed, as there are already 3 methyl groups on the carbon on the end. Carbon can only form up to 4 bonds, and so the reaction from alcohol to alkene is not possible here.

 

[KZW]

What will react differently with the two isomeric pentanols, (CH3)3CCH2OH and (CH3)2CHCH2CH2OH?
A acidified aqueous potassium manganate(VII)
B concentrated sulphuric acid
C phosphorus pentachloride
D sodium

Why is it B? Both are primary alcohol, should it both become Alkene?

(CH3)3CCH2OH will not dehydrate into an alkene. The reason being is that there can't be a double bond formed, as there are already 3 methyl groups on the carbon on the end. Carbon can only form up to 4 bonds, and so the reaction from alcohol to alkene is not possible here.

 

[ZaqZainab]

A tiny doubt i just started my AS but i can't understan what Azimuthal means i tried google still don't get it Can anyone help ASAP

 

[MemoryMatrix 21]

What are the exact 2 graphs of heterogenous catalysis??

 

[sanisha 1234]

will anyone tell me about the tips of paper 5 n dependent ,independent variable

 

[MemoryMatrix 21]

will anyone tell me about the tips of paper 5 n dependent ,independent variable

Ya............independent variable is da one u r changing n dependent variable is a 1 that is supposed 2 b kept constant!
Independent variable is plotted on x-axis n dependent variable on y-axis!

 

[1357911]

Aoa.
http://papers.xtremepapers.com/CIE/... AS Level/Chemistry (9701)/9701_w10_qp_41.pdf
Q-4 c??

 

[Dr.MMM]

Two equilibria are shown below.

reaction I 2X2(g) + Y2(g) gives 2X2Y(g)
reaction II X2Y(g) gives X2(g) + 1/2Y2(g)

The numerical value of Kc for reaction I is 2.

Under the same conditions, what is the numerical value of Kc for reaction II?
answer is 1/under root 2

EXPLAIN HOW

 

[salvatore]

http://papers.xtremepapers.com/CIE/... AS Level/Chemistry (9701)/9701_w11_qp_42.pdf
Could someone please explain qn no. 3(c) - the whole of it. I don't know how to solve it
Pleaseee!!

 

[Jinosupreme]

31 Which statements are correct in terms of the Brønsted-Lowry theory of acids and bases?
1 Water can act as either an acid or a base.
2 Sulfuric acid, H2SO4, does not behave as an acid when dissolved in ethanol, C2H5OH.
3 The ammonium ion acts as a base when dissolved in liquid ammonia.

Answer is 1 only, why?

 

[Jinosupreme]

Which reaction will give 2-chloropropane in the best yield?
A propane gas with chlorine gas in the presence of ultraviolet light
B propan-2-ol with dilute NaCl (aq)
C propan-2-ol with SOCl 2
D propene with dilute HCl (aq)

I chose D, why cannot? Answer is C.

 

[Jinosupreme]

The products obtained by cracking an alkane, X, are methane, ethene and propene.

The mole fraction of ethene in the products is 0.5.

What is the identity of X?
A C6H14
B C8H18
C C9H20
D C11H24

Answer is B. I don't really understand the question, what does it mean the mole fraction of ether is 0.5? Pls help thanks!

 

[Jinosupreme]

I chose A, why cant? Answer is B




Answer is D, I understand why it is structural isomer, but donno why osmotic pressure increase.

Answer is A.

Why??

 

[Jinosupreme]

Which pairs of homologous series have the same C:H ratio in their general formulae?
1 aldehydes and ketones
2 carboxylic acids and esters
3 alkenes and ketones

Answer is 1,2,3

Help :O

 

[Musab100]

any can help me plz ?????

http://papers.xtremepapers.com/CIE/... AS Level/Chemistry (9701)/9701_w12_qp_11.pdf

MCQs :

11
15
17
23
30
33

 

[Jessie N.]

A solution of Sn2+ ions will reduce an acidified solution of MnO4– ions to Mn2+ ions. The Sn2+ ions are oxidised to Sn4+ ions in this reaction.
How many moles of Mn2+ ions are formed when a solution containing 9.5 g of SnCl 2 (Mr: 190) is added to an excess of acidified KMnO4 solution?

help plzzzzzz

 

[snowbrood]

A solution of Sn2+ ions will reduce an acidified solution of MnO4– ions to Mn2+ ions. The Sn2+ ions are oxidised to Sn4+ ions in this reaction.
How many moles of Mn2+ ions are formed when a solution containing 9.5 g of SnCl 2 (Mr: 190) is added to an excess of acidified KMnO4 solution?

help plzzzzzz

these quations are given in data booklet so no need to memorize it
Sn2+⇌ Sn4++ 2e- equation 1
(MnO4–)+ (8H+)+ 5e– ⇌ (Mn2+)+ 4H2O) equation 2
balance the number of electrons so that each equation have same number of electrons
multiply equation 1 by 5 and equation 2 by 5
and then add these equations we get
(16H+)+(5Sn2+)+2MnO4- yields (5sn4+)+2Mn2+
ignore the liquid we are concerned with ions and ions only
2moles of mno4- reacts with 5moles of sn2+
2/5moles of mn 1 moles sn
(9.5/190)*2/5 9.5/190

 

[snowbrood]

31 Which statements are correct in terms of the Brønsted-Lowry theory of acids and bases?
1 Water can act as either an acid or a base.
2 Sulfuric acid, H2SO4, does not behave as an acid when dissolved in ethanol, C2H5OH.
3 The ammonium ion acts as a base when dissolved in liquid ammonia.

Answer is 1 only, why?

actually u might know water is amphoteric oxide and sulfuric acid is an acid this settles it i think u might be confused with 3
ammonia is base as it accepts protons however ammonium ion nh4+ cant accept any protons rather it will donate protons behaving as an acid.
u can also sum it up like what was once acid after dissociating it will be base. and likewise