Biology; Chemistry; Physics: Post your doubts here!

[asadalam]

 

[exploded diper]

explaination for both plz......17:d and 18:a

 

[Awesome12]

View attachment 39276
explaination for both plz......17:d and 18:a

17) a- adding more catalyst only increases rate of reaction
b- This will favour backward reaction, as greater no. of moles are on reactant's side
c- Reaction is exothermic, and backward reaction will be favoured
That leaves us with d

18) Only these salts can be made by titration method:
Ammonium salts
Potassium
Calcium
Sodium

 

[exploded diper]

17) a- adding more catalyst only increases rate of reaction
b- This will favour backward reaction, as greater no. of moles are on reactant's side
c- Reaction is exothermic, and backward reaction will be favoured
That leaves us with d

18) Only these salts can be made by titration method:
Ammonium salts
Potassium
Calcium
Sodium

ohhhhkay thhxxxx......

 

[Jenn]

Explain this to me, someone?

 

[Awesome12]

Explain this to me, someone?

Initially, p.d across the capacitor is minimum, and current is maximum. As the capacitor charges, it stores charges,and the p.d across it increases, and the current decreases. When the capacitor is fully charged, p.d across it is max, which is equivalent to the emf of the cell, and the current is 0

 

[Jenn]

Initially, p.d across the capacitor is minimum, and current is maximum. As the capacitor charges, it stores charges,and the p.d across it increases, and the current decreases. When the capacitor is fully charged, p.d across it is max, which is equivalent to the emf of the cell, and the current is 0

Thank you!

 

[asadalam]

Initially, p.d across the capacitor is minimum, and current is maximum. As the capacitor charges, it stores charges,and the p.d across it increases, and the current decreases. When the capacitor is fully charged, p.d across it is max, which is equivalent to the emf of the cell, and the current is 0

So basically,it sucked all the power out of the cell?

 

[funky brat]

http://papers.xtremepapers.com/CIE/...al O Level/Chemistry (5070)/5070_w09_qp_1.pdf
Someone explain MCQ 14.
Other than this MCQ, In an exothermic reaction, more bonds are broken than are formed, is that right?

 

[Awesome12]

So basically,it sucked all the power out of the cell?

yup

 

[Awesome12]

http://papers.xtremepapers.com/CIE/Cambridge International O Level/Chemistry (5070)/5070_w09_qp_1.pdf
Someone explain MCQ 14.
Other than this MCQ, In an exothermic reaction, more bonds are broken than are formed, is that right?

This is the most confusing thing in Chem. In another question like this the answer was More energy needed to break bonds... It is just weird.
The explanation to this is that we do not know how many bonds are being formed than are broken. No reaction is given or nothing. Just the statement, 'The reaction is exothermic'. We already know that more energy is released than absorbed in an exothermic reaction. We also know that one material's bonds are stronger when it requires more heat to break the bonds. Thus from this we can conclude that Bonds formed in exothermic reactions are much stronger, and thus release more heat than is absorbed to break the bonds.
Hence the answer is D

 

[funky brat]

This is the most confusing thing in Chem. In another question like this the answer was More energy needed to break bonds... It is just weird.
The explanation to this is that we do not know how many bonds are being formed than are broken. No reaction is given or nothing. Just the statement, 'The reaction is exothermic'. We already know that more energy is released than absorbed in an exothermic reaction. We also know that one material's bonds are stronger when it requires more heat to break the bonds. Thus from this we can conclude that Bonds formed in exothermic reactions are much stronger, and thus release more heat than is absorbed to break the bonds.
Hence the answer is D

Alright. Thanks.

 

[funky brat]

http://papers.xtremepapers.com/CIE/...al O Level/Chemistry (5070)/5070_w09_qp_1.pdf
In the 6th MCQ, the last option, why is that wrong?

 

[Maganius]

http://papers.xtremepapers.com/CIE/...al O Level/Chemistry (5070)/5070_w09_qp_1.pdf
In the 6th MCQ, the last option, why is that wrong?

Because Graphite also has weak forces of attraction b/w its layers.

 

[funky brat]

Because Graphite also has weak forces of attraction b/w its layers.

Yeah, there are weak Van Der Walls forces of attraction, but what bonds are they?

 

[Maganius]

Yeah, there are weak Van Der Walls forces of attraction, but what bonds are they?

I don't think so we classify Van Der Walls forces as bonds.

 

[funky brat]

I don't think so we classify Van Der Walls forces as bonds.

Alright. Thanks.

 

[Awesome12]

http://papers.xtremepapers.com/CIE/...al O Level/Chemistry (5070)/5070_w09_qp_1.pdf
In the 6th MCQ, the last option, why is that wrong?

Covalent bonding results in electron sharing. However, there are some free electrons in Graphite, indicating there is some other form of bonding (metallic) that allows it to exhibit metallic characteristics as well

 

[funky brat]

Covalent bonding results in electron sharing. However, there are some free electrons in Graphite, indicating there is some other form of bonding (metallic) that allows it to exhibit metallic characteristics as well

Well, nobody ever told me there is metallic bonding in Graphite.

 

[Awesome12]

Well, nobody ever told me there is metallic bonding in Graphite.

I just derived that