Chemistry: Post your doubts here!

[geek101]

Hey guys need help with this!!
View attachment 8916

only one (the answer is B) any carbon with a double bond or two similar groups like CH2 cant be chiral. so the only one is the CH with the benzene ring attached to it.

 

[geek101]

http://www.xtremepapers.com/papers/... AS Level/Chemistry (9701)/9701_w11_qp_12.pdf someone plz!

 

[samwickz]

Skiers trapped by snowstorms use heat packs to keep warm. The heat may be generated by the
reaction below.
4Fe(s) + 3O2(g) → 2Fe2O3(s) ; ∆HO = –1648kJ
What is the standard enthalpy change of formation of iron(III) oxide?

A 0kJmol–1
B –824kJmol–1
C –1648kJmol–1
D –3296kJmol–1

helppppppppppppppppppppppppp!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

 

[angelicsuccubus]

Hey guys need help with this!!
View attachment 8916

I don't see any..

 

[saudha]

you still have this problem or its solved now...???

solved... thxxx

 

[user]

Hey guys need help with this!!
View attachment 8916

aoa wr wb!

1
cuz benzene has none..other carbon has either some double bonds..or more than one hydrogen attached..
its the one attached to CH2 and a benzene ring

 

[smartangel]

Hey guys need help with this!!
View attachment 8916

answer?

 

[KurayamiKimmi]

Skiers trapped by snowstorms use heat packs to keep warm. The heat may be generated by the
reaction below.
4Fe(s) + 3O2(g) → 2Fe2O3(s) ; ∆HO = –1648kJ
What is the standard enthalpy change of formation of iron(III) oxide?

A 0kJmol–1
B –824kJmol–1
C –1648kJmol–1
D –3296kJmol–1

helppppppppppppppppppppppppp!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

since the enthalpy change of formation of 2 moles of iron(III) oxide is -1648 the standard enthalpy change of formation of 1 mole of iron(III) oxide will be the half which is B

 

[Goku]

Oxidation no. of N is -3.
Oxidation no. of H is +1.
Oxidation no. of O is -2.
Sum of oxidation no.s in a compound must equal zero.

When you calculate it, C is the only option.

Because, look:

NH4ClO4 -> -3+4+x-8=0
-> 1+x-8=0
-> -7+x=0
->x=7

oh my gosh,you explained it so well! Thankyou!!!!

 

[Casablanca]

Skiers trapped by snowstorms use heat packs to keep warm. The heat may be generated by the
reaction below.
4Fe(s) + 3O2(g) → 2Fe2O3(s) ; ∆HO = –1648kJ
What is the standard enthalpy change of formation of iron(III) oxide?

A 0kJmol–1
B –824kJmol–1
C –1648kJmol–1
D –3296kJmol–1

helppppppppppppppppppppppppp!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

What on Earth is "∆HO"?

 

[cHeStEr]

http://www.xtremepapers.com/CIE/International A And AS Level/9701 - Chemistry/9701_w06_qp_1.pdf
question 9 Plzzz......

thnks in advnce....

 

[samwickz]

since the enthalpy change of formation of 2 moles of iron(III) oxide is -1648 the standard enthalpy change of formation of 1 mole of iron(III) oxide will be the half which is B

OMG thank u sooooooooooooooooooooo freaking much!

 

[Casablanca]

http://www.xtremepapers.com/CIE/International A And AS Level/9701 - Chemistry/9701_w06_qp_1.pdf
question 9 Plzzz......

thnks in advnce....

I think the answer is C. Check in marking scheme if this is correct. If so, I'll explain what I did.

 

[samwickz]

What on Earth is "∆HO"?

delta H theta

 

[Casablanca]

delta H theta

Ah, okay.

 

[samwickz]

Ah, okay.

 

[cHeStEr]

I think the answer is C. Check in marking scheme if this is correct. If so, I'll explain what I did.

Yup its correct

 

[KurayamiKimmi]

OMG thank u sooooooooooooooooooooo freaking much!

no problem

 

[Casablanca]

Yup its correct

Okay, here goes:

CO2(g) + H2(g) -> CO(g) + H2O(g)

CO2 is being broken, so instead of -283, we take +283
H2O is being formed, so we use -286
BUT it is being formed in gaseous state, not liquid state, so we also take +44.

283 + 44 - 286 = +41.

So the answer is C.

 

[Goku]

http://www.xtremepapers.com/CIE/International%20A%20And%20AS%20Level/9701%20-%20Chemistry/9701_s03_qp_1.pdf


^ question 7 please? :/