Chemistry: Post your doubts here!

[Sahan27]

how to find the other element

View attachment 53315

Its Bromine
Cos M+2 peak and M peak are of the same height
if the ratio between the M+2 and the M peak are the same its always Bromine

 

[princessnoor]

2nd last question was kinda tricky!!

The organic one? Yh

 

[Suchal Riaz]

You can try viewing it from the end on the left side. Then visualize them as clock faces, using references with H and CH3 at the 12 o'clock positions.

View attachment 53391

oh that makes it much easier. I had no teacher so i deduced that method of mine myself.

 

[_Ahmad]

can anyone please explain Q2 (e) and (f) of this paper
http://onlineexamhelp.com/wp-content/uploads/2015/02/9701_w14_qp_52.pdf

 

[Ch.Walid]

Here's a great video explaining trends in the periodic table.

Trends in the periodic table

 

[randomcod]

w09 qp 5
If anyone can have a look at it... From what point do we consider it to be 'higher temperature', and from what point do we consider it 'lower temperature'?

 

[ashcull14]

In an experiment, 50.0 cm3 of a 0.10 mol dm–3 solution of a metallic salt reacted exactly with
25.0cm3 of 0.10moldm–3 aqueous sodium sulphite. The half-equation for oxidation of sulphite ion is shown below.
SO3^2− (aq) + H2O(I) → SO4^2− (aq) + 2H+(aq) + 2e–
If the original oxidation number of the metal in the salt was +3, what would be the new oxidation
number of the metal?

 

[ashcull14]

 

[princess Anu]

View attachment 53733

If you find the ratio of salt to sulphite( simply by finding moles of salt and sulphite according to the info given) it comes out to be 2:1
& the equation shows 1 mole of sulphite looses 2 electron, therefore 2 mol of metallic salt gain those 2 electrons or 1 mol of metallic salt gains 1 mol of electron
therefore new O.N. of metal = +3-1=+2!

 

[princess Anu]

somebody help
ans is C

 

[princess Anu]

this too
ans is C

 

[lara dalal]

Hello. How do i do this? The answer is D

 

[Mohammad Farzanullah]

in chem p5, why is it necessary that the line of best fit passes through the origin?

 

[princess Anu]

Hello. How do i do this? The answer is D
View attachment 53745

for the mercury level to rise at right end, the pressure being exerted from gases in bulb R should increase!
Now in option 1,if temp is increased, forward reaction is favoured, and will lead to the formation of 2 moles of the gas which will inturn exert greater pressure. However in option 2, there are equal no of moles on both sides of the equilibrium so even if as temp is increased backward reaction may be favoured but it'll not cause an INCREASE in pressure.

 

[lara dalal]

How do we do this? The answer is A

 

[ashcull14]

If you find the ratio of salt to sulphite( simply by finding moles of salt and sulphite according to the info given) it comes out to be 2:1
& the equation shows 1 mole of sulphite looses 2 electron, therefore 2 mol of metallic salt gain those 2 electrons or 1 mol of metallic salt gains 1 mol of electron
therefore new O.N. of metal = +3-1=+2!

thnk u SO much that was very helpful indeed <3

 

[ashcull14]

 

[ashcull14]

 

[lara dalal]

View attachment 53805

H3PO4 is generally not an oxidising agent thats why options A and B are wrong. For option C, During the reaction of NaCl and H2SO4, HCl (the acidic gas) is formed, if H2SO4 was a stronger oxidising agent it would go on and form the yellow/green gas of Cl2. but it didnot hence it is NOT a stronger oxidising agent. If H2SO4 was a stronger oxidising agent it would have Completely oxidised the Cl- to Cl2. For D NaI Reacts with H2SO4 to form HI, the HI is further oxidised by the H2SO4 to form the purple vapour of iodine; the I- got oxidised to I2 This shows that H2SO4 IS in. fact a stronger oxidising agent than iodine

 

[princess Anu]

View attachment 53806

Simply, the rate of formation of ppt shows the rate of reaction.. The order given shows that Iodobutane has the greatest rate. This implies that breaking of I- C bond takes place fastest of all .. meaning bond strength / energy of C-I is lowest