Chemistry: Post your doubts here!

[mustafa5255]

is option A correct answer?

YESSSS, but how?

 

[Hamnah Zahoor]

YESSSS, but how?

For this you will have to learn the ionisation energy graph given in the book and know that in the first period highest ionisation energy is that of noble gases and when we shift to the next the ionisation energy decreases by a great extent. As H+ is invloved the other element is from group 7

 

[mustafa5255]

For this you will have to learn the ionisation energy graph given in the book and know that in the first period highest ionisation energy is that of noble gases and when we shift to the next the ionisation energy decreases by a great extent. As H+ is invloved the other element is from group 7View attachment 65306

 

[mustafa5255]

Omg!! Thank you so muchhh!!!

 

[Hamnah Zahoor]

Omg!! Thank you so muchhh!!!

No problem

 

[Madina2410]

At this temperature water also exist as gas so also add up the volume of water.

Thank you , that’s what I thought 😂

 

[ptet.chemistry]

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[Filth1212]

Please help!

YESSSS, but how?

is option A correct answer?

As the question states they are in ascending atomic number, however they are not all in the same period.
The greatest ionisation energy for any period belongs to the noble gases, hence B is a noble gas therefore as A is before B A is a halogen.

 

[easchemistry12]

X, Y and Z are three elements in the third period.
● X reacts with chlorine to give a liquid product.
● Y reacts with chlorine to give a solid product that dissolves in water to give a
solution of pH 7.
● Z reacts with chlorine to give a solid product that dissolves in water to give a solution
of pH 6.
Which elements are good conductors of electricity?

 

[easchemistry12]

A solution contains both Mg2+(aq) and Sr2+(aq) at the same concentration.
The solution is divided into two equal portions. Aqueous sodium hydroxide is added dropwise to
one portion. Dilute sulfuric acid is added dropwise to the other portion.
Which row is correct?

 

[Mr.Physics]

X, Y and Z are three elements in the third period.
● X reacts with chlorine to give a liquid product.
● Y reacts with chlorine to give a solid product that dissolves in water to give a
solution of pH 7.
● Z reacts with chlorine to give a solid product that dissolves in water to give a solution
of pH 6.
Which elements are good conductors of electricity?

X is definitely Si which reacts with chlorine to give SiCl4, a colourless liquid at r.t.p.

Y is Na which reacts with chlorine to give NaCl that dissolves in water to give a solution of pH 7.

Z is Mg which reacts with chlorine to give MgCl2 that dissolves in water to give a slightly acidic solution with pH 6.

Finally, only Na and Mg are the good electrical conductors among these elements.

 

[Mr.Physics]

A solution contains both Mg2+(aq) and Sr2+(aq) at the same concentration.
The solution is divided into two equal portions. Aqueous sodium hydroxide is added dropwise to
one portion. Dilute sulfuric acid is added dropwise to the other portion.
Which row is correct?

I think you didn't post the complete question. Do upload a SS from the question paper and I'll try to solve it 😁

 

[easchemistry12]

thanks i got that.............

 

[easchemistry12]

Compound X produces a carboxylic acid when heated under reflux with acidified
potassium dichromate(VI). Compound X does not react with sodium metal.
What could be the identity of compound X?
A propanal
B propanone
C propan-1-ol
D propan-2-ol

answer is propanal but why?

 

[Mr.Physics]

Compound X produces a carboxylic acid when heated under reflux with acidified
potassium dichromate(VI). Compound X does not react with sodium metal.
What could be the identity of compound X?
A propanal
B propanone
C propan-1-ol
D propan-2-ol

answer is propanal but why?

I mostly use the process of elimination to reach the correct answer for these type of questions.
Firstly, propanone won't oxidise to a carboxylic acid because it is a ketone, so we can eliminate B right from the start.
Now you must know that metals like Na, Mg react very well with alcohols (primary or secondary) to give bubbles of H2 gas and alkoxide anion + metal cation. Therefore, we can eliminate C and D too. Since we're left with A, it must be the correct answer.

 

[easchemistry12]

thank u

 

[easchemistry12]

thank u

 

[ptet.chemistry]

Hello guys, if you always find chemistry P1 MCQs tricky, perhaps my step-by-step tutorial videos can help. If you like what my channel offers, please subscribe and share with friends/colleagues/relatives. It is a not-for-profit channel and I am simply a full time chemistry teacher wanting to reach out to help as many as possible.

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[easchemistry12]

Ms says correct answer is D can anyone please help me with justification of answer and why option A is not correct?

 

[ptet.chemistry]

If Kc increases at higher temperature, the forward reaction must have absorbed more heat energy to shift to the right. That means forward reaction is favoured. I would go for A.

IF D is correct, that would potentially mean how Kc remains constant, but that would also mean temperature cannot be changing, so I won't really think it is D.