Chemistry: Post your doubts here!

[UMRASDE]

Which solid contains more than one kind of bonding?
A. Iodine
B. Silicon dioxide
C. Sodium chloride
D. Zinc

The answer is A but I don't understand really why. I know that it has covalent bonds and van der waals forces, but don't silicon dioxide and sodium chloride also have those?

Which element is likely to have an electronegativity similar to that of aluminium?
A. barium
B. beryllium
C. magnesium
D. strontium
I have no clue as to how to figure this one out

Suggest an explanation for the existence of IF7 and for the non-existence of ClF7? The answer says because I is a bigger atom than Cl but I need a more thorough explanation as I didn't understand anything from that answer.

Thank you

silicon dioxide has a giant molecular structure and consist of only strong covalent bomd

 

[UMRASDE]

Can someone tell me why the answer is B

 

[Rahul Pat]

Please help me with this question!

 

[❤Nouran❤]

Please help me with this question!

I guess it is C

 

[Jean Lim]

in an experiment a sample of a pure gas is put into a gas syringe at a temperature of 300K and pressure of 16 kpa. the gas is compressed until the volume occupied by the gas is halved.
after the compression, the temperature of the gas in syringe is 375 and the pressure is 40 kpa.
is the gas is ideal

The gas is behaving ideally, use PV=nRT before and after compression and make n the subject. You'll see that for both equations n is constant.

 

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[examhelpbd]

Hi everyone, AsSalamoAlaikum Wr Wb..

To get things organized in a better way, I am making this thread. As othewise, some queries remain unanswered!

So post your CHEMISTRY doubts in this thread. InshaAllah members around will help you.

Any Chemistry related notes and links will be added here in this post. Feel free to provide the links to your notes around the forum, or any other websites!

Chemistry Notes:


http://www.chemguide.co.uk This is the website, which contains almost everything classified according to the syllabus.

Tips for solving chemistry MCQs 9701/01

Chemistry P5 Tips and Notes

Some links & Notes - by 'destined007'

Chemistry worksheets Link shared by hassam

Chemistry Application Booklet: Mistakes and Corrections!

Calculations for A level Chemistry, author E.N. Ramsden third edition ebook download.


Regards,
XPC Staff.

I want to help my type of confusion.

 

[examhelpbd]

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[Jenpen]

In Kc we do not take the concentration of the solid. So in this case we will not include the concentration of Ag(s)
So it will be as follows:
Kc= (0.56) / (0.44^2)
= 2.89
That's option D

where did u get 0.56 from lol

 

[zophiel]

where did u get 0.56 from lol

They got it by subtracting 0.44 mol from 1 mol

 

[romeopoomore]

Can someone plsss tell how to balance this equation by oxidation number?

Helping those who come tomorrow 😊 ...
We can balance it using the balancing in alkaline conditions thus we get

 

[Madina2410]

Hi can you explain why the enthalpy change of neutralisation of one mole of sulfuric acid, H2SO4, is not the standard enthalpy change of neutralisation.

 

[romeopoomore]

Hi can you explain why the enthalpy change of neutralisation of one mole of sulfuric acid, H2SO4, is not the standard enthalpy change of neutralisation.

Because of the term 'standard' which tells us the conditions which the neutralisation occurs in . The enthalpy change of any reaction is dependent on the conditions which the reaction occurs in . The standard enthalpy change refers to when the concentration of the sulfuric acid and the base are at 1 moldm^-3 and the temperature which the reaction occurs in at 25 degrees Celsius and the sulfuric acid in its most standard state which is when it is dissolved in water. When such things are altered they change the enthalpy change of neutralisation to give a slightly different value.
I don't know if I have answered you but I hope I have

 

[Madina2410]

CH4(g) + 2O2(g) CO2(g) + 2H2O(l) ∆H = -890 kJmol-1

what’s the entalphy of formation of methane

 

[Madina2410]

Th

Because of the term 'standard' which tells us the conditions which the neutralisation occurs in . The enthalpy change of any reaction is dependent on the conditions which the reaction occurs in . The standard enthalpy change refers to when the concentration of the sulfuric acid and the base are at 1 moldm^-3 and the temperature which the reaction occurs in at 25 degrees Celsius and the sulfuric acid in its most standard state which is when it is dissolved in water. When such things are altered they change the enthalpy change of neutralisation to give a slightly different value.
I don't know if I have answered you but I hope I have

thank you

 

[romeopoomore]

CH4(g) + 2O2(g) CO2(g) + 2H2O(l) ∆H = -890 kJmol-1

what’s the entalphy of formation of methane

Hello .We would need the enthalpy change of formation of carbon dioxide and water so we may draw a hess cyclee diagram since we are not told that the reaction is performed at standard conditions and cannot just blindly assume

 

[Madina2410]

Ex

Hello .We would need the enthalpy change of formation of carbon dioxide and water so we may draw a hess cyclee diagram since we are not told that the reaction is performed at standard conditions and cannot just blindly assume

exactly😂 I thought the same way because this question was given by my teacher and I thought I’m missing out something

 

[Madina2410]

I

Hello .We would need the enthalpy change of formation of carbon dioxide and water so we may draw a hess cyclee diagram since we are not told that the reaction is performed at standard conditions and cannot just blindly assume

have a question , what’s the purpose of drawing the Hess’a cycle if we can directly do the subtraction method