Biology; Chemistry; Physics: Post your doubts here!

[gary221]

Don't tell me you knew that before the paper. Anyone can google after the paper. There is nothing binding in the CIE Syllabus. They can easily give something new and expect us to do it. What I am basically asking for is that if someone has any colour chart given by a teacher or someone it would be helpful

Excuse me?
Just FYI, I have already appeared for both Chemistry IGCSE and A-levels, so as it turns out, I did know that before the said paper. Also, if you think the only was people actually know stuff is by googling it, why dont you simply do it yourself?
And a tiny reminder.

 

[***amd***]

http://papers.xtremepapers.com/CIE/Cambridge International O Level/Chemistry (5070)/5070_s13_qp_22.pdf

B10, c part. (i).

the actual eq. is
NaCl (aq) + AgNO3 (aq) ----------> AgCl (s) + NaNO3 (aq)
ionic eq.
Na+(aq) + Cl-(aq) + Ag+(aq) + NO3-(aq) ----------> AgCl (s) + Na+(aq) + NO3-(aq)

we cut of the ions which are in aq state on both sides.
we get
Ag+(aq) + Cl-(aq) --------> AgCl (s)

 

[***amd***]

This may be way too dumbo.

But isn't AgCl an ionic bond too or something?

Also - is there any other metal other than aluminium that has this unreactive oxide layer over it ?

AgCl is ionic bond, but we convert to ions only those bonds which are in aq. state. and AgCl is in solid state (ppt)

i dunno .-.

 

[Dark Destination]

What is the effect of ozone in the lower atmosphere?

 

[***amd***]

What is the effect of ozone in the lower atmosphere?

reacts with unburnt hydrocarbons and produces photochemical smog that causes headache.

 

[Dark Destination]

reacts with unburnt hydrocarbons and produces photochemical smog that causes headache.

What exactly is photo-chemical smog?
Does ozone cause breathing difficulties?

 

[***amd***]

What exactly is photo-chemical smog?
Does ozone cause breathing difficulties?

tbh, me nay ratta lagaya hai. i dunno what it actually is .-.
smog causes irritation in eys, nose n throat

ozone also corrodes and kills plants.

 

[Laibaaa]

do metals react with water to form metal oxides or hydroxides? :|

 

[Dark Destination]

do metals react with water to form metal oxides or hydroxides? :|

Depends on the metal. Reactive metals react to form Hydroxides. Some don't even react with water, like Magnesium. They only react with steam.

 

[***amd***]

Is MgO & MgOH soluble or insoluble? Coz one notes I got says Ca to Ba - other says entire GrpII.

group 1 oxides are completely soluble, and group 2 oxides are partially soluble.
only oxides of first 4 of reactivity series and oxide of ammonium are soluble.

 

[***amd***]

in neutralisation reaction, why does pH goes too high? i mean why isnt it neutralised?
eg.
if base is added to acid, why does pH goes from acidic to baic? why not neutral at 7?

 

[Laibaaa]

Metal reacts with water = hydroxide.
Metal reacts with steam = oxide.
This is because the metal hydroxides thermally decompose (split up on heating) to give the oxide and water.

thankyouu. And this goes for all right? Like all the metals in the reactivity series?

 

[Dark Destination]

Wrong. (That feels strange )

Mg reacts. :3 very Slowly - but it does. Zinc and Iron etc se start hota hai only steam reactions

Really?

Magnesium reacts with water? :O

But i read it reacts with steam .-.

 

[***amd***]

I know that. What I am asking is strictly oxide and hydroxide solubility here. Is MGOH or MGO water soluble? Simple yes/no answer please.

MgO is partially soluble, MgOH is completely soluble.

 

[***amd***]

Really?

Magnesium reacts with water? :O

But i read it reacts with steam .-.

no, it doesnt! it only reacts with steam!

 

[***amd***]

My book (Chem Insights) says it does :/ Ah well.

my teacher's notes say, it doesn't.

 

[Dark Destination]

How to draw dot and cross diagrams of ionic compounds to show outer shell only? Do we show 8 electrons in sodium ion or empty shell?

 

[***amd***]

How to draw dot and cross diagrams of ionic compounds to show outer shell only? Do we show 8 electrons in sodium ion or empty shell?

8 electrons of sodium.

 

[Laibaaa]

would someone please explain if changes of state are exothermic or endothermic?:|

 

[Laibaaa]

T

Endo: Bond Breaking - S --> L --> G
Exo: Bond Formation - G --> L --> S

Thankyouu very much!