Chemistry: Post your doubts here!

[Metanoia]

yeah but the ans is D :/

Hmm..I reread the question, now I understand your confusion. Seems to me both A and D are possible answers. This is a past year question?

 

[princess Anu]

y not D

 

[princess Anu]

yup its N2014/11

but is NaAlOh4 considered a salt?

Hmm..I reread the question, now I understand your confusion. Seems to me both A and D are possible answers. This is a past year question?

 

[princess Anu]

how to decide between Nacl and MgO about which one will have a higher M.P/B.P

 

[Metanoia]

yup its N2014/11

but is NaAlOh4 considered a salt?

Yes. NaAlOH4 is a salt.

I'm surprised it can react with cold NaOH.

But having reread the question and having to choose between Al2O3 and SiO2, I guess SiO2 is more unreactive due to its giant covalent structure.

 

[nehaoscar]

How to solve this??
Answer is B

 

[nehaoscar]

How to do this one??

 

[nehaoscar]

How to do this?
Answer is B

 

[nehaoscar]

Why won't bromine react?

 

[The Sarcastic Retard]

View attachment 54154

How to do this?
Answer is B

 

[The Sarcastic Retard]

View attachment 54153

How to solve this??
Answer is B

C3H7OH + 4.5O2 --> 3CO2 + 4H2O
0.1 mol of acid was burned.
0.45 mol of oxygen used.
Volume of oxygen = 0.45 x 24 = 10.8 dm^3
Volume of CO2 = 7.2 dm^3 (ratio)
Initial volume of oxygen = 12 dm^3
12 - 10.8 = 1.2dm^3 left
Dont forget to add 7.2dm^3 of co2.
1.2+7.2 = 8.4dm^3

 

[lara dalal]

View attachment 54155

Why won't bromine react?

there is no C=C for the Br2 to react with. Incase you thought it would react with OH, it wouldnt cause the bromine needs to be added as NaBr and heated with H2SO4 so it can react with alcohol, simple aqueous bromine cannot react with OH

 

[Metanoia]

View attachment 54153

How to solve this??
Answer is B

Create a balance equation on the combustion.

Figure out which is the limiting reactant and what gases of CO2 and O2 you have left over.

 

[lara dalal]

How to do this one??

for option 1
62/100*74 =45.88 of butan-2-ol actually reacted to form butanone. The number of moles of the reacted butan-2-ol are hence 45.88/74(Mr of butan-2-ol) = 0.62 moles. The number of moles of alcohol reacted will be equal to number of moles of ketone formed. Hence mass of butanone is 0.62 moles*72= 44.64g Hence statement 1 is correct.
For option 3
again 62% of 74g is 45.88g of the alcohol hence the number of moles will be 45.88/74(Mr of 2-methyl alcohol)=0.62 moles. As moles of reactant in this case is equal to moles of product, the mass of acid is 0.62*88= 54.56g. Hence statement 3 is correct. If 1 and 3 are correct the answer is for sure A

 

[lara dalal]

I never understood how to know which one has more/less overall dipole. Can anyone explain this to me? The answer is D

 

[The Sarcastic Retard]

View attachment 54156
I never understood how to know which one has more/less overall dipole. Can anyone explain this to me? The answer is D

This question is pretty easy. 2EN (Cl) are in diagonals which cancels each other out, in no other option there u see EN elements in diagonal hence D

 

[Metanoia]

View attachment 54156
I never understood how to know which one has more/less overall dipole. Can anyone explain this to me? The answer is D

The Cl atoms are electronegative, look for the symmetry, D has the Cl pulling the electrons in opposite directions and canceling each other out.

 

[lara dalal]

The Cl atoms are electronegative, look for the symmetry, D has the Cl pulling the electrons in opposite directions and canceling each other out.

Arent the Cl atoms in option B also pulling in opposite directions? or does that count as the same direction?

 

[The Sarcastic Retard]

Arent the Cl atoms in option B also pulling in opposite directions? or does that count as the same direction?

It should be in diagonals. In B overall DPM is +---->

 

[Metanoia]

Arent the Cl atoms in option B also pulling in opposite directions? or does that count as the same direction?

Imagine the molecule flat on a table.

Visualise placing your fingers where the Cl atoms are and apply a pulling force.

You should be able to see that molecule B "moves upwards" (due to an overall dipole moment) , whereas molecule D remains stationary.

Its analogous to forces in physics.