Chemistry: Post your doubts here!

[nehaoscar]

 

[ciephobia]

Whoa i wasn't taught this! Does this apply to all elements?

don't worry, it is not a big chapter but covers some concepts.
just read about it here: http://www.chemguide.co.uk/atoms/bonding/electroneg.html on the bottom of the page.

 

[nehaoscar]

I know it's +2 with cold but how is it -1 with hot?

 

[nehaoscar]

Why is 2 incorrect?

 

[ciephobia]

View attachment 54432

is it D?

 

[nehaoscar]

How is 1 correct?
N goes from +3 to 0 only ... no other change so show redox??

 

[nehaoscar]

is it D?

Yes
How?

 

[nehaoscar]

How is 1 correct
and 2 and 3 wrong?

 

[ciephobia]

Yes
How?

because

• 2NaBr(s) + 2H2SO4(l) ==> NaHSO4(s) + Br2(g) + SO2(g) + 2H2O(l)
  acid is a proton (hydrogen) donor and NaBr went to NaHSO4, gaining a hydrogen.
• oxidation also occured as The oxidation state of bromine changes from –1 in Br–, to 0 in Br2 (oxidation, increase in oxidation state)

 

[qwertypoiu]

Could you please explain a bit more?
I mean like the others are not polar either right?

Ethanol and water are polar .
The option D has to do with freezing not melting.

 

[qwertypoiu]

View attachment 54436
How is 1 correct
and 2 and 3 wrong?

Ca is 2+. The CH3CO2- ion is -1.
So two organic ions are required per Ca2+ ion.

 

[phanttasy]

1 mol of (NH4)2CO3 has 2 moles of nitrogen atoms so O.65 moles will have 1.3 moles of nitrogen ATOMS
and O.65* (14*2+ 8+12+16*3) = 62.4 g of this compound give us 1.3 moles of nitrogen atoms...

This is what I think.. Lets c what others say

Oh.. I see... Is it also means that 1 mole of (NH4)2CO3 has 3 mole of oxygen atoms/ 1 mole of carbon/ 8 mole of carbon atoms?

 

[qwertypoiu]

View attachment 54434
Why is 2 incorrect?

Effective collision refers to collisions with sufficient energy to react. Since temperature did not change, there is no change to proportion of such collisions.

 

[qwertypoiu]

View attachment 54435
How is 1 correct?
N goes from +3 to 0 only ... no other change so show redox??

Cl went from -1 to +1 (in OCl- ion)

 

[ciephobia]

Effective collision refers to collisions with sufficient energy to react. Since temperature did not change, there is no change to proportion of such collisions.

hey, sorry to disturb you but can you help me with this?
thanks in advance.

 

[qwertypoiu]

View attachment 54433
I know it's +2 with cold but how is it -1 with hot?

The OH group on the left gets oxidised to CO2H group.
CO2H group makes this previously chiral carbon non chiral. So -1

Edit: sorry it's secondary so it'll make a ketone but same answer still.

 

[qwertypoiu]

hey, sorry to disturb you but can you help me with this?
thanks in advance.

The precipitate is Ca(OH)2. It's only very partially soluble so will form a white solid. After filtration only Ba(OH)2 remains in high concentration. The barium hydroxide reacts with CO2 to form a white ppt, BaCO3

 

[ciephobia]

The precipitate is Ca(OH)2. It's only very partially soluble so will form a white solid. After filtration only Ba(OH)2 remains in high concentration. The barium hydroxide reacts with CO2 to form a white ppt, BaCO3

God bless you.

 

[Mathemagical]

View attachment 54433
I know it's +2 with cold but how is it -1 with hot?

The secondary alcohol group on the left will be oxidised to a ketone group, so there will be one less chiral centre.

 

[nehaoscar]

Cl went from -1 to +1 (in OCl- ion)

But then it's asking for nitrogen so don't you only look at the nitrogens?