Chemistry: Post your doubts here!

[darknessinme]

http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Chemistry (9701)/9701_s11_qp_12.pdf

Q 11 you guys,It's been asked here for like 3 times and apparently it wasn't answered . can someone answer it for me ?
Can't think of an answer!


11 0.144 g of an aluminium compound X react with an excess of water, to produce a gas. This gas
burns completely in O2 to form H2O and 72 cm3
of CO2 only. The volume of CO2 was measured at
room temperature and pressure.

What could be the formula of X?
A Al 2C3 B Al 3C4 C Al 4C3 D Al 5C3

https://www.xtremepapers.com/community/threads/chemistry-mcq-thread.7567/page-82

I answered it there.

 

[darknessinme]

Help >~< Can someone explain it to me please???

With cold you get addition of two alcohol groups at double bond, so both the carbons involved in the double bond become chiral carbons, thus +2.
With hot, you get cleavage of the double bond, producing a ketone group and carboxylic acid group, however the don't turn into chiral carbons. Carbon attached to alcohol group on far left is chiral, but the OH gets oxidised to ketone, so carbon is no longer chiral, thus -1.
Answer: D

 

[immie.rose]

I urgently need the answers to the End-of-chapter questions of Cambridge Chemistry Coursebook. Can somebody PLEASE pass em on? Pretty Please?

 

[Browny]

If possible please answer the following and if possible leave out all the periodicity questions, questions on groups and on nitrogen and sulphur because I haven't gone through them and don't know whether the questions are from those units. Please do answer the other questions including the one on contact process and haber process.



http://papers.xtremepapers.com/CIE/...d AS Level/Chemistry (9701)/9701_w06_qp_1.pdf

Q5, Q11, Q17, Q19, Q31

http://papers.xtremepapers.com/CIE/...d AS Level/Chemistry (9701)/9701_w07_qp_1.pdf

Q5, Q6, Q9, Q21, Q32, Q35, Q36, Q37

http://papers.xtremepapers.com/CIE/...d AS Level/Chemistry (9701)/9701_s06_qp_2.pdf

Q1) a) iii)

Q2) e) ii)

Q4) c)
e)

http://papers.xtremepapers.com/CIE/...d AS Level/Chemistry (9701)/9701_w06_qp_2.pdf

Q5) d)
f)

 

[Kinki Tiffany 12]

http://papers.xtremepapers.com/CIE/... AS Level/Chemistry (9701)/9701_s10_qp_11.pdf

can anyone help me with question 4, 10 and 11 ?

 

[Khadija_1234]

Sorry for my poor English and handwriting ˊ_>ˋ hope you can understand.

Thank you so much

 

[Jessie N.]

With cold you get addition of two alcohol groups at double bond, so both the carbons involved in the double bond become chiral carbons, thus +2.
With hot, you get cleavage of the double bond, producing a ketone group and carboxylic acid group, however the don't turn into chiral carbons. Carbon attached to alcohol group on far left is chiral, but the OH gets oxidised to ketone, so carbon is no longer chiral, thus -1.
Answer: D

Thankyouuuuu

 

[Jinosupreme]

Answer is B. Why answer can't be D? It is also correct right?

 

[Jinosupreme]

How to do? Answer is D

 

[Jinosupreme]

An element X and compound YZ react separately with acid as shown.
X(s) + 2H+(aq) → X2+(aq) + H2(g)
YZ(s) + 2H+(aq) → Y2+(aq) + H2Z(g)
When 1.0 g of either X or YZ is reacted with an excess of acid, the total volume of gas formed is the same.
Which statements are correct?
1. Ar(X) = Mr(YZ)
2. X and Y are metals.
3. X and Y must both be in the same Group of the Periodic Table.

Answer is 1 & 2 why?

 

[*MK*skydiver :D]

https://www.xtremepapers.com/community/threads/chemistry-mcq-thread.7567/page-82

I answered it there.

Thank you ! I really appreciate it

 

[*MK*skydiver :D]

visit here：http://www.assignmentexpert.com/free-questions/question-on-chemistry-physical-chemistry-5313.html
or ：http://sgforums.com/forums/2297/topics/443584

both have some explanations，but I think we can get the answer by common sense: Al has ox. no of 3+ and C is 4- ?

hahahaha, common sense doesn't always work with Chemistry there are alwaaaysss exceptions !

*complications , complications*

Thank you for the answers; helpful

 

[Jessie N.]

hahahaha, common sense doesn't always work with Chemistry there are alwaaaysss exceptions !

*complications , complications*

Thank you for the answers; helpful

LOL so true

 

[Jessie N.]

Answer is B. Why answer can't be D? It is also correct right?

For D，the first and the second one is the same. Try to draw out the displayed formula then you will notice it.

 

[Jinosupreme]

A solution of Sn2+ ions will reduce an acidified solution of MnO – 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?
A 0.010
B 0.020
C 0.050
D 0.125

How to do? Answer is B

 

[x-gamer-x]

A solution of Sn2+ ions will reduce an acidified solution of MnO – 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?
A 0.010
B 0.020
C 0.050
D 0.125

How to do? Answer is B

Sn2+ + MnO4- –––––> Sn4+ + Mn2+
ox. no. of sn is increased by 2 (it is oxidized to Sn4+) which means 2 electrons are removed Sn2+ ----> S24+ + 2e
ox. no. of Mn in MnO4- is +7 and in Mn2+ is 2+ so it is reduced means 5 e are added MnO4- + 5e ----> Mn2+
to balance mult. with 5 to the Sn2+ equ.
and 2 wtih MnO4- equ.
u will get 5Sn2+ ----> 5Sn4+ + 10e
2MnO4- + 10e ----> 2Mn2+
adding equtions u will get
5Sn2+ + 2MnO4- ----> 2Mn2+ + 5Sn4+
from equ. Ratio is 5 : 2 so 9.5g which is (0.05moles) of Sn2+ will reduce 0.05 * 2 / 5 = 0.02
Ans B

 

[Jinosupreme]

Solids W, X, Y and Z are compounds of two different Group II metals. Some of their applications
are described below.
Compound W is used as a refractory lining material in kilns.
Compound X is used as a building material. It can also be heated in a kiln to form compound Y. When Y is hydrated, it forms compound Z which is used agriculturally to treat soils.
Which statements about these compounds are correct?
1 More acid is neutralised by 1g of W than by 1g of X.
2 The metallic element in W reacts with water more quickly than the metallic element in Y.
3 Adding Z to a soil decreases the pH of the soil.

Answer is 1 only why?

 

[Jinosupreme]

An organic compound, Z, will react with calcium metal to produce a salt with the empirical formula
CaC4H6O4.
What could be the identity of Z?
1 ethanoic acid
2 butanedioic acid
3 methylpropanedioic acid

Answer is 1 only. Why?

 

[x-gamer-x]

An organic compound, Z, will react with calcium metal to produce a salt with the empirical formula
CaC4H6O4.
What could be the identity of Z?
1 ethanoic acid
2 butanedioic acid
3 methylpropanedioic acid

Answer is 1 only. Why?

no
ans is 2 and 3
so its C

 

[snowbrood]

An organic compound, Z, will react with calcium metal to produce a salt with the empirical formula
CaC4H6O4.
What could be the identity of Z?
1 ethanoic acid
2 butanedioic acid
3 methylpropanedioic acid

Answer is 1 only. Why?