Physics, Chemistry and Biology: Post your doubts here!

[R_Ma7mooD]

Guys for the exam do we need to memorize like bond energies and things like those, cuz its kinda impossible..

 

[hard_worker]

ANYONE PLZ!

 

[princess sofia]

http://papers.xtremepapers.com/CIE/Cambridge IGCSE/Chemistry (0620)/0620_s04_qp_1.pdf
Q32
how is it A , aluminium forms an oxide layer , how cn it be corroded heavily?

 

[princess sofia]

View attachment 43375

ANYONE PLZ!

 

[R_Ma7mooD]

http://papers.xtremepapers.com/CIE/Cambridge IGCSE/Chemistry (0620)/0620_s04_qp_1.pdf
Q32
how is it A , aluminium forms an oxide layer , how cn it be corroded heavily?

Since aluminum is more reactive than steel, it will be corroded in preference to it. So aluminum loose electrons in preference to the iron to prevent the iron from forming Iron Oxide.
This is used to prevent corrosion in ships. By using a block of zinc attached to the ship's iron surface.. Zinc corrodes in preference to iron..

 

[Xylferion]

Since aluminum is more reactive than steel, it will be corroded in preference to it. So aluminum loose electrons in preference to the iron to prevent the iron from forming Iron Oxide.
This is used to prevent corrosion in ships. By using a block of zinc attached to the ship's iron surface.. Zinc corrodes in preference to iron..

Basically sacrificial protection right?

 

[R_Ma7mooD]

Basically sacrificial protection right?

exactly , I forgot the name

 

[Xylferion]

exactly , I forgot the name

Have you come across any challenging questions btw? I'm looking for some.

 

[R_Ma7mooD]

Have you come across any challenging questions btw? I'm looking for some.

hmmm this one:
http://papers.xtremepapers.com/CIE/Cambridge IGCSE/Chemistry (0620)/0620_s10_qp_31.pdf

qs 4

 

[princess sofia]

cn any1 explain me , the reactivity series , which one cn oxidise which one ,
Xylferion

 

[Xylferion]

hmmm this one:
http://papers.xtremepapers.com/CIE/Cambridge IGCSE/Chemistry (0620)/0620_s10_qp_31.pdf

qs 4

What's hard about that? :O

 

[princess sofia]

Basically sacrificial protection right?

bt isnt aluminium havng protective oxide layer which makes it unreactive?

 

[princess sofia]

hmmm this one:
http://papers.xtremepapers.com/CIE/Cambridge IGCSE/Chemistry (0620)/0620_s10_qp_31.pdf

qs 4

i was doing the same paper , its nt so challengng all u need is an active mind

 

[Xylferion]

bt isnt aluminium havng protective oxide layer which makes it unreactive?

That's when there is no other metal present. Here aluminium is more reactive than steel. So it sacrifices itself, to protect steel.

 

[ChubbyBunny]

I don't understand why prop-1-ene or 2-ene is named I genrally understand the alkenes tho :/

 

[gary221]

I don't understand why prop-1-ene or 2-ene is named I genrally understand the alkenes tho :/

Depending on the position of the double bond.
For eg, in butene. If the double bond is btw the 1st and 2nd carbon, it is but-1-ene. Btw 2nd and 3rd carbon = but-2-ene.

 

[esshven]

Chemistry exams in 3 hours . Good luck everyone

 

[slisjunknown]

I don't understand why prop-1-ene or 2-ene is named I genrally understand the alkenes tho :/

It depends on the position of the Carbon double bond which occurs. In case u havent still got it, bring it to scul;I'll tell u

 

[slisjunknown]

Please help guyz I've got a doubt in the question no. 5 c(i)
http://papers.xtremepapers.com/CIE/Cambridge IGCSE/Chemistry (0620)/0620_w13_qp_31.pdf

 

[Phoenix Blood]

k.e. = g.p.e.
so 1/2mv^2 = hmg right?
so if mass increases by same amount on both sides, with v constant, height stays the same.
Flawed, twisted logic perhaps, but that was my answer.

And force is inversely proportional to distance only when work/energy is constant. But since g.p.e. is increasing too, I don't think this holds.

I don't care now I'm dumb at Phy.