Chemistry: Post your doubts here!

[loveyuan]

Sorry but I hav

Sorry I cant help you, because I havnt done the applications part. I thought you were talking about the electrolysis part. So sorry I couldnt help you.Hope you find what your looking for.
btw have you complete the A2 syllabus.

Yeah completed . I have A2 exam coming soon .

 

[Wolfgangs]

Can someone please answer and explain each part? I'm still not understanding how to use equations in relation to moles.

 

[Yogita.T]

http://papers.xtremepapers.com/CIE/... AS Level/Chemistry (9701)/9701_w10_qp_31.pdf

Hi can someone please help solve the numericals of this paper?

Specifically Q1 - c... (i) (ii) (iii) (iv)
Thanks

 

[Metanoia]

Can someone please answer and explain each part? I'm still not understanding how to use equations in relation to moles.

ii) moles of KOH used = vol. of KOH solution x conc. of KOH solution = 0.01 dm^3 x 2 mol dm^-3 = 0.02 mol

iii) from equation
mol of Al : mol of KOH
2 : 2

Therefore, 0.02 mol of KOH would react with 0.02 mol of Al.

iii) mass of Al reacted = moles of Al x Ar of Al = 0.02 x 27 = 0.54 g

 

[Neoh Kai Qin]

9701 ON01 Marking Scheme?!!???

 

[mustaf]

when testing for salts are we supposed to shake the test tube to make the salt dissolve o will dissolve by its self

 

[Awesome12]

Why do the 3d orbitals have more energy than the 4s orbitals? I do know that it is due to the Auf-Bau Principal, but if such a question comes in the exam, what explanation am I supposed to give?

 

[asadalam]

Why do the 3d orbitals have more energy than the 4s orbitals? I do know that it is due to the Auf-Bau Principal, but if such a question comes in the exam, what explanation am I supposed to give?

Is it in the syllabus?

 

[Awesome12]

Is it in the syllabus?

I don't know.

 

[princess Anu]

Can somebody please help me with these MCQ's:
nov 04
question 34 : Why isn't 1 correct too? The tips represent Noble gases right? and Group 8 can be called Group 0, no?
May 05
Question 3 : Why isn't it D? ( answer is C)
Question 14
Nov 05
Q3 , 14

 

[DeViL gURl B)]

Hey guys,
I'm looking for some summary sorta notes for the last 3 Alevels chapters that are:

-> chemistry of life
-> Application of analytic chemistry
-> Design and material
I'm mostly weak in the section B of paper 4
It'd be of great appreciation to get any help
Thank you

 

[Metanoia]

Can somebody please help me with these MCQ's:
nov 04
question 34 : Why isn't 1 correct too? The tips represent Noble gases right? and Group 8 can be called Group 0, no?
May 05
Question 3 : Why isn't it D? ( answer is C)
Question 14
Nov 05
Q3 , 14

Nov 04
Qn 34: The marking scheme says all statements are correct. So statement 1 is also correct.

May 05
Qn 3: Element in D belongs to Group V (the huge increase in IE is from the 5th to the 6th IE)

Qn14: Reactivity of Group II metals increases down the group , calcium is more reactive than magnesium.

 

[princess Anu]

Thankyou, would you please explain Q13 of May June 05 and those of Nov 05 too?

 

[zohaib6199]

Does Any one have notes for as level chemistry practical notes orli

 

[RoOkaYya G]

yeah its given in data booklet. ull get for Cl2 for Cl uve to divide the value by 2 normally

 

[Metanoia]

Thankyou, would you please explain Q13 of May June 05 and those of Nov 05 too?

Nov 05.
Qn3. The easiest way is first figure out the respective elements in the four options, then refer to the 2nd IEs in IE table in the data booklet.

A. Mg (compare its 2nd IE to Na and Al)
B. Al (compare its 2nd IE to Mg and Si)
C. Si (compare its 2nd IE to Al and P)
D. P (compare its 2nd IE to Si and S)



You can see that Al has a higher 2nd IE compared to its neighbours Mg and Si.

Qn 14. Again, use the data booklet.
"Element Y has the highest first ionisation energy " means that we can eliminate options B and C, leaving us with option A and D.
" Element Y has lowest melting point." means we can eliminate A (as sodium has a lower melting point than magnesium).
So we are left with D.
P has a lower melting point than Si (giant molecular structure) and S (stronger VDW forces)

A sodium, magnesium, aluminium
B magnesium, aluminium, silicon
C aluminium, silicon, phosphorus
D silicon, phosphorus, sulphur

May 05
Qn 13: Be and Al has similar electronegativity, this is the diagonal relation in the Periodic Table.
You can read a discussion on it in the paragraph "what is a diagonal relationship" in this link.
Other pairings are Li and Mg, B and Si.

 

[Anallia]

Can somebody please help me with Q1 (b) and Q2 (c) of the attached files? Incase of Q2 (c), how do we get to know the standard enthalpy change of atomisation of Chlorine? Where is it given in the data booklet?

use the bond energy for Cl-Cl bond given in the data booklet

 

[huh]

Can someone please help me with testing for gases during practical. How do we test for all the gases before all the gas has been liberated?

 

[Bilal Khan]

Can someone please help me with testing for gases during practical. How do we test for all the gases before all the gas has been liberated?

It's written in the last two pages of every practical , the identification of ions and gases . Ammonia turns moist red litmus blue .

 

[huh]

It's written in the last two pages of every practical , the identification of ions and gases . Ammonia turns moist red litmus blue .

Yes but whenever I do the test for gases, take burning splint and so on, all the gas liberates and I have mix the solutions again. Any way to prevent this? Thank you for replying.