Biology; Chemistry; Physics: Post your doubts here!

[usama321]

my book says, "Silicon oxide melts only at high temperatures. This is because the silicon and oxygen are held tightly together by strong covalent bonds in the network" is this correct? i thought melting point is related to van der waal's forces
usama321

normally simple covalent bonded compounds have low melting point. Silicon oxide has high cuz it has a huge covalent bonding structure, with a lot of covalent bonds, which makes it stronger than normal covalent compounds

 

[HDIWAN]

Please anyone differentiate Diamond with Graphite...

in graphite atoms are arranged in layers while in diamond are closely packed


in graphite each carbon atom is bonded to 3 other atoms while in diamond each is bonded to 4 other atoms

in diamond atoms are tetrahedrally arranged while in graphite are arranged in rings/hexagonal arrangement

graphite have some delocalised/mobile electrons while diamond dont have mobile electrons

diamond have strong covalent bonds between all the atoms while graphite contains weak forces between the layers

 

[sohaib Ahmes]

in graphite atoms are arranged in layers while in diamond are closely packed and regularly arranged

in graphite each carbon atom is bonded to 3 other atoms while in diamond each is bonded to 4 other atoms

in diamond atoms are tetrahedrally arranged while in graphite are arranged in rings/hexagonal arrangement

graphite have some delocalised/mobile electrons while diamond dont have mobile electrons

diamond have strong covalent bonds between all the atoms while graphite contains weak forces between the layers

do you have imran merchant chemistry gurss paper?

 

[farhan141]

Ionic Equations (Notes) Please.

 

[sohaib Ahmes]

Ionic Equations (Notes) Please.

do uou have merchant chemistry guess paper?

 

[farhan141]

do uou have merchant chemistry guess paper?

do uou have merchant chemistry guess paper?

No I don't and please stop spamming,

 

[HDIWAN]

no

do you have imran merchant chemistry gurss paper?

 

[usama321]

in graphite atoms are arranged in layers while in diamond are closely packed and regularly arranged

I don't think the atoms in diamond are regularly arranged

 

[chocolate_girl]

yep, maybe 10 mins or so

Alright a short one like not of half an hour

 

[HDIWAN]

I don't think the atoms in diamond are regularly arranged

my apologies

 

[farhan141]

http://papers.xtremepapers.com/CIE/...al O Level/Chemistry (5070)/5070_s08_qp_1.pdf

Q.24. Why can't number 1 statement be true?

Also, explain or provide notes of Oxidising and Reducing Agents. I am always confused b/w them. Someone help please. Everyone's answers are appreciated.

 

[Saad Mughal]

Catalyst enhances both the back and forward reaction so equilibrium remains the same

The catalyst simply helps to reach equilibrium quickly, since time is money in industry, it is helpful.

 

[papajohn]

http://papers.xtremepapers.com/CIE/Cambridge International O Level/Chemistry (5070)/5070_s08_qp_1.pdf

Q.24. Why can't number 1 statement be true?

Also, explain or provide notes of Oxidising and Reducing Agents. I am always confused b/w them. Someone help please. Everyone's answers are appreciated.

barium chloride is salt. Its not a neutralisation reaction .

 

[Saad Mughal]

http://papers.xtremepapers.com/CIE/Cambridge International O Level/Chemistry (5070)/5070_s08_qp_1.pdf

Q.24. Why can't number 1 statement be true?

Also, explain or provide notes of Oxidising and Reducing Agents. I am always confused b/w them. Someone help please. Everyone's answers are appreciated.

Acids are confirmed by the following properties:
- pH (lower than 7).
- Reactions with Metals, Metal Oxides/Hydroxides, Metal Carbonates.
So, the answer is D.

Oxidizing Agents:
-Acidified Potassium Dichromate (VI), KCr2O7, it OXIDIZES other compounds and itself is REDUCED, the oxidation state of the Cr ions changes from +6 to +3 (gain of electron). The colour change is from Orange [Cr (+6)] to Green [Cr (+3)].
-Acidified Potassium Manganate (VII), KMnO4, it OXIDIZES other compounds and itself is REDUCED, the oxidation state of the Mn ions changes from +7 to +2 (gain of electron). The colour change is from Purple to Colourless.

Reducing Agents:
-Aqueous Potassium Iodide, KI, it REDUCES other compounds and is itself OXIDIZED, the oxidation state of the I ion changes from -1 to 0. The colour change is from colourless to brown.
-Sulphur Dioxide, SO2, it REDUCES other compounds and is itself OXIDIZED, no colour change.

 

[Saad Mughal]

Do oxides of more reactive metals always form hydroxides when reacted with water and carbonates when reacted with carbon dioxide?

Yes they do, when the more reactive metal oxides from Potassium Oxide to Aluminium Oxide react with water they form Metal Hydroxides.
However, this depends on their reactivity and solubility, aluminium oxide is sparingly soluble and less reactive so the reaction is rather slow.
For carbonates, I don't know for sure. But, other than Sodium and Potassium, all the other carbonates decompose on heating to Metal Oxide + Carbon Dioxide, I don't know whether the reverse reaction is true or not.

 

[Amnaa]

how can i find limiting reagent in the equation..??

 

[Saad Mughal]

Do oxides of more reactive metals always form hydroxides when reacted with water and carbonates when reacted with carbon dioxide?

I googled the second part, it is true. The metal oxide undergoes synthesis reaction with carbon dioxide to form metal carbonate.

 

[farhan141]

Acids are confirmed by the following properties:
- pH (lower than 7).
- Reactions with Metals, Metal Oxides/Hydroxides, Metal Carbonates.
So, the answer is D.

Oxidizing Agents:
-Acidified Potassium Dichromate (VI), KCr2O7, it OXIDIZES other compounds and itself is REDUCED, the oxidation state of the Cr ions changes from +6 to +3 (gain of electron). The colour change is from Orange [Cr (+6)] to Green [Cr (+3)].
-Acidified Potassium Manganate (VII), KMnO4, it OXIDIZES other compounds and itself is REDUCED, the oxidation state of the Mn ions changes from +7 to +2 (gain of electron). The colour change is from Purple to Colourless.

Reducing Agents:
-Aqueous Potassium Iodide, KI, it REDUCES other compounds and is itself OXIDIZED, the oxidation state of the I ion changes from -1 to 0. The colour change is from colourless to brown.
-Sulphur Dioxide, SO2, it REDUCES other compounds and is itself OXIDIZED, no colour change.

Can you explain Reduction and Oxidation too? Please this is killing me

 

[farhan141]

http://papers.xtremepapers.com/CIE/...al O Level/Chemistry (5070)/5070_s08_qp_1.pdf

Same Paper. Q.33. Explain what happens through the processes please. Thanks in Advance!

 

[Saad Mughal]

how can i find limiting reagent in the equation..??

Find the moles ratio using the equation.
Calculate the number of moles of each reactant by the given mass/volume.
The reactant that has the greater quantities of moles than required for the reaction (by mole:mole ratio) is in excess. The other one is the limiting agent.