Chemistry: Post your doubts here!

[$$AK$$]

hi guys,
where could i find all the chemical reactions with their condition that i should know in chemistry 9709 (AS) for examination in 2014 ???
Help is highly appreciated

 

[1357911]

I never said that the anomalous points will be used to calculate the gradient ...i was saying that eg ...we have drawn a line ....and there are some points (points from the table)which lies accurately on the line ...and then its not allowed to draw the triangle using those particular points bcz even if the ans gets correct even then the marks are penalized for that.

phir?? which points do we have to take then?

 

[Hassan Ali Abid]

phir?? which points do we have to take then?

koi bhi points ..which are on the line except those points on the line which are already present in the table ...

 

[1357911]

koi bhi points ..which are on the line except those points on the line which are already present in the table ...

to what did i say?? -.- I was saying the exact same thing.

 

[Hassan Ali Abid]

to what did i say?? -.- I was saying the exact same thing.

but see ur fig and the triangle which u have drawn .....u have used the points from the table to draw the triangle ...isnt it ???

 

[1357911]

but see ur fig and the triangle which u have drawn .....u have used the points from the table to draw the triangle ...isnt it ???

I get what u are trying to say now, but My teacher never mentioned this point.

 

[Ahmed Aqdam]

http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Chemistry (9701)/9701_s03_qp_1.pdf
Question 8

Remember: Oxygen always has oxidation state -2 and hydrogen +1 (except metal hydrides e.g.NaH). Every uncombined element has zero oxidation number

A: Nitrogen has +3 oxidation number in NH3 which reduces to -2 in NO. The change is 5.
B: Oxidation number of nitrogen is +4 in NO2 and +5 in HNO3 as in the NO3- ion Oxygen has total of -6 so the ion has -1. The change is 1.
C: +2 in NO and +4 in NO2. Change is 2.
D: -3 in NH3 and +2 in NO.Zero in N2. Biggest change is 3.

Hence the greatest change is in A (5).

 

[KWIKIW]

6 Three compounds have the physical properties shown in the table.

compound P Q R
melting point / °C 2852 993 –119
boiling point / °C 3600 1695 39
conductivity (solid) poor poor poor
conductivity (liquid) good good poor
conductivity (aqueous) insoluble good insoluble


What might be the identities of P, Q and R?

P Q R
A MgO KCl NH3
B MgO NaF C2H5Br
C SiO2 KCl C2H5Br
D SiO2 NaF HCl


35 When a firework is lit, a fuel and an oxidising agent react together.

In one such firework, magnesium is the fuel and barium nitrate is the oxidising agent.

Which solids are produced when the firework is lit?
1 BaO
2 MgO
3 Mg(NO3)2

What are the correct statements?


36 In a car engine, non-metallic element X forms a pollutant oxide Y.

Further oxidation of Y to Z occurs spontaneously in the atmosphere. In this further oxidation,
1 mol of Y reacts with 0.5 mol of gaseous oxygen.

Which statements about X, Y and Z are correct?
1 The oxidation number of X increases by 2 from Y to Z.
2 The molecule of Y has no unpaired electrons.
3 The molecule of Z contains three oxygen atoms.

What are the correct statements?

 

[KWIKIW]

This is the complete question.

 

[A star]

Any one here for chem and/or p5 inbox me or just tag me here ill inbox you we can prep togetherand help each other(over xpf) cause i guess the old ones who used to help arent active anymore :/

 

[sara kamal]

http://papers.xtremepapers.com/CIE/...d AS Level/Chemistry (9701)/9701_w06_qp_4.pdf

please explain Q2 c(3)
will be very thankful !

 

[Browny]

http://papers.xtremepapers.com/CIE/... AS Level/Chemistry (9701)/9701_w11_qp_12.pdf

Can anyone please explain Q35, Q36?

 

[yousef]

Paper5- mj2009
q 1(e) ..& if someone can even do second question graph and share it with us that will be much appreciated.

 

[M Haseeb Javed]

How do you find pH of a buffer solution?

 

[ritesh isuri]

help me plz with this: A solutiion A is saturated with both calcium hydroxide and calsium sulphate. both are sparingly soluble. a)pH of A is 12.3 find concentration of OH-.
b) Ksp of calsium hydroxide =4.0*10^-5, find concentration of calcium ions in A
c)Ksp of calcium sulphhate is 2.5*10^-5, find conc of sulphate ions in A.

 

[halloffame]

well thanks for ur help but I only need from chapter 17-30 and in pdf format

In the CD ROM folder Go to the following folder and select the pdf belonging to there respective chapters :

CHEMISTRY _ AS & A CD ROM\AS and A Level Chemistry CB\source_data\Answers_questions

 

[halloffame]

well thanks for ur help but I only need from chapter 17-30 and in pdf format

Here is the .ZIP file containing the answers from chap 17 to 13. Hope it will help u. .>>>>>> Hit LIKE

PASSWORD : chem

 

[danial 234]

can any1 answer this???
are HCl, HBr, HI strong acids in aqueous solutions??

 

[danial 234]

6 Three compounds have the physical properties shown in the table.

compound P Q R
melting point / °C 2852 993 –119
boiling point / °C 3600 1695 39
conductivity (solid) poor poor poor
conductivity (liquid) good good poor
conductivity (aqueous) insoluble good insoluble


What might be the identities of P, Q and R?

P Q R
A MgO KCl NH3
B MgO NaF C2H5Br
C SiO2 KCl C2H5Br
D SiO2 NaF HCl


35 When a firework is lit, a fuel and an oxidising agent react together.

In one such firework, magnesium is the fuel and barium nitrate is the oxidising agent.

Which solids are produced when the firework is lit?
1 BaO
2 MgO
3 Mg(NO3)2

What are the correct statements?


36 In a car engine, non-metallic element X forms a pollutant oxide Y.

Further oxidation of Y to Z occurs spontaneously in the atmosphere. In this further oxidation,
1 mol of Y reacts with 0.5 mol of gaseous oxygen.

Which statements about X, Y and Z are correct?
1 The oxidation number of X increases by 2 from Y to Z.
2 The molecule of Y has no unpaired electrons.
3 The molecule of Z contains three oxygen atoms.

What are the correct statements?

6) ans is B
cz R is liquid at rtp and according to choices.. bromoethane is liq so ans must be C or B..... and as P conducts electricity in liq state so it must be ionic that is Mgo..
so ans is B

35) in fireworks reactions, metal oxides are produced not metal nitrate so ans becomes B 1 &2

36) it says that further oxidation occurs spontaneously so X must be N, Y be NO...and Z be NO2.....
1 is correct cz in NO, N has ox state +2 and in NO2 it has +4
2 is wrong cz there are unpaired electron in molecule of No
3 is wrong cz NO2 has 2 oxygen atoms

 

[sidbloom1995]

i have a doubt in october november 2010 p41 question 4 part c iii n iv
can anyone answer it?