Chemistry: Post your doubts here!

[Aries_95]

The reaction between aluminium powder and anhydrous barium nitrate is used as the propellant
in some fireworks. The metal oxides and nitrogen are the only products.
Which volume of nitrogen, measured under room conditions, is produced when 0.783 g of
anhydrous barium nitrate reacts with an excess of aluminium?
A 46.8cm3
B 72.0cm3
C 93.6cm3
D 144cm3
Help !

2Al+Ba(NO3)2--->Al2O3+Bao+N2
Mole of Ba(NO3)2= 0.783/(261)=3x10^-3 mole
Mole of N2=mole of Ba(NO3)2= 3x10^-3 mole
1 mole--->24 dm^3
3x10^-3= 24x(3x10^-3)=0.072 dm^3
0.072dm^3=72 cm^3.
the answer is B. right?

 

[zackle09]

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

can someone please do question 10 and 40

 

[darkxangel]

2Al+Ba(NO3)2--->Al2O3+Bao+N2
Mole of Ba(NO3)2= 0.783/(261)=3x10^-3 mole
Mole of N2=mole of Ba(NO3)2= 3x10^-3 mole
1 mole--->24 dm^3
3x10^-3= 24x(3x10^-3)=0.072 dm^3
0.072dm^3=72 cm^3.
the answer is B. right?

yes it is and thanks again

 

[darkxangel]

An organic compound J reacts with sodium to produce an organic ion with a charge of –3.
J reacts with NaOH(aq) to produce an organic ion with a charge of –1.
What could be the structural formula of J?
A HO2CCH(OH)CH2CO2H
B HO2CCH(OH)CH2CHO
C HOCH2CH(OH)CH2CO2H
D HOCH2COCH2CHO
Help !

 

[imperial]

An organic compound J reacts with sodium to produce an organic ion with a charge of –3.
J reacts with NaOH(aq) to produce an organic ion with a charge of –1.
What could be the structural formula of J?
A HO2CCH(OH)CH2CO2H
B HO2CCH(OH)CH2CHO
C HOCH2CH(OH)CH2CO2H
D HOCH2COCH2CHO
Help !

I think C. (Na can react with both -CO2H and OH, there is 3 in C so -3 but NaOH only with -CO2H so -1) I'm not sure though as I didn't revise from a long time.

I have a question : http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Chemistry (9701)/9701_w11_qp_11.pdf

Number 9, the answer is D but I don't know how to get it.

 

[Alice123]

I think C. (Na can react with both -CO2H and OH, there is 3 in C so -3 but NaOH only with -CO2H so -1) I'm not sure though as I didn't revise from a long time.

I have a question : http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Chemistry (9701)/9701_w11_qp_11.pdf

Number 9, the answer is D but I don't know how to get it.

Kc of solids cannot be found... ignore the Ag(s) n then find kc

 

[Sara syed]

Pls explain s10 qp13 question 13,23, w11 qp 12 qs. 12 and 39

 

[daisyy]

hey can anyone PLEASE HELP ME WITH question 18 in may/june 2007, question 37 in oct/nov 2006 and question37 in oct/nov 2007!! Thanks guys!

 

[Alice123]

http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Chemistry (9701)/9701_w11_qp_11.pdf
Q6 h4rriet Jinkglex

 

[h4rriet]

http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Chemistry (9701)/9701_w12_qp_11.pdf
Q.17 plz!
h4rriet

Find the moles of O2 using n=v/24 (don't forget to convert cm3 to dm3). Then write down the equations for the combustion of all the metals. Calculate the moles of all the metals using n=m/Ar. Then use mole ratios.

 

[Sara syed]

in s10 qp13 question 30 what r the three alkenes that btan2 ol can produce on dehydration i know its's but1-ene and but2-ene what is the third one?

 

[Alice123]

A reaction which causes the presence of oxides of nitrogen in car exhausts is the formation of
NO.
N2 + O2→ 2NO ∆H = +180kJmol–1
What is the bond energy in kJmol–1 of the bond between the atoms in NO?
A 655 B 835 C 1310 D 1670

PLEASE SOLVE AND EXPLAIN THIS QUESTION!

which year?

 

[Alice123]

Use bonds broken - bonds formed.

details please

 

[h4rriet]

http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Chemistry (9701)/9701_w11_qp_11.pdf
Q6 h4rriet

2 moles of one compound is broken down. So divide the energy by 2. And then divide what you get by the number of bonds in the molecule.

 

[h4rriet]

in s10 qp13 question 30 what r the three alkenes that btan2 ol can produce on dehydration i know its's but1-ene and but2-ene what is the third one?

It's a cis-trans isomer.

 

[Alice123]

2 moles of one compound is broken down. So divide the energy by 2. And then divide what you get by the number of bonds in the molecule.

cud u please quote values of bonds broken and formed...

 

[HubbaBubba]

More help please!

 

[h4rriet]

cud u please quote values of bonds broken and formed...

No, forget about the bonds broken - bonds formed; you can't do it that way. Only ONE compound is made, so all the bonds made are its own, and all the energy of the reaction goes to it and it alone. There are 2 moles of it, so the energy it used to make 2 compounds. To find the energy needed to make 1 mole, divide the energy needed to make 2 moles by 2. (It's given in the question). Now you have the energy needed to make 1 compound. You need to get the energy needed to break the bonds in that 1 compound. The number of bonds in the compound is 3, so you divide the energy by 3.

 

[Raiyan3]

Yet again im posting please do help
" Question number 7 please help
http://papers.xtremepapers.com/CIE/... AS Level/Chemistry (9701)/9701_s12_qp_12.pdf
And question number 11 and 23
http://papers.xtremepapers.com/CIE/... AS Level/Chemistry (9701)/9701_s11_qp_12.pdf "

 

[Jinkglex]

cud u please quote values of bonds broken and formed...

i believe the answer is A, first of all you see that 500K will give more K.E to the molecules, so D is out. Then since fraction of molecules cant be more then original, B is out. Finally, according to Boltzmann distribution laws the curve will become shorter and have a less sharp peak, so C is out, because the peaks are equal in C which isn't possible.