Chemistry: Post your doubts here!

[princess Anu]

Why is option 2 correct?? I know it is true, but how is it even related to the theory? please help

 

[alevelpleasebegood]

For this question, the correct answer is B. However, I got the answer A...
My working steps are:
K2O+H2O->2KOH
2KOH+H2SO4->K2SO4+2H2O
Found the no of moles for H2SO4, which is 0.03 mol, then used mole ratio and got the no of moles for KOH, which is 0.06 mol
I then used mole ratio and found no of moles for K2O, 0.03 moles
Mass of K2O=o.o3 mol X Mr K2O
=2.83 .....

http://postimg.org/image/vd4jealez/

 

[shazmina]

C isn't balanced. 4 O in reactants, 5 in products.

apart from balancing, is there any other concept behind the answer B?

 

[Mathemagical]

View attachment 54575
Why and how D?
If it's D then the Carbon before the R will only have 3 bonds :O
Why not B?

Since it does not have cis-trans isomers, the two groups on the right side of the C=C bond must be identical. C has 4 bonds: one double bond and two of them to the C2H5 groups.

 

[Mathemagical]

Why is option 2 correct?? I know it is true, but how is it even related to the theory? please help

Option 2 is incorrect. Sulfuric acid can act as an acid because the oxygen atom in ethanol has two lone pairs, either of which can accept the proton.

 

[shazmina]

Help please ........
http://s11.postimg.org/980xvhyv7/table.jpg
The Ans is A......

 

[shazmina]

Help please ........

The conversion of graphite has only a small positive value of H.

C (graphite) ---------> C (diamond) H = +2.1 kJ mol –1

However, the production of synthetic diamonds using this reaction is very difficult.

Which statements help to explain this?

1 The activation energy of the reaction is large.

2 An equilibrium exists between diamond and graphite.

3 Only exothermic reactions can be made to occur readily.

The Ans is D

 

[qwertypoiu]

Help please ........

The conversion of graphite has only a small positive value of H.

C (graphite) ---------> C (diamond) H = +2.1 kJ mol –1

However, the production of synthetic diamonds using this reaction is very difficult.

Which statements help to explain this?

1 The activation energy of the reaction is large.

2 An equilibrium exists between diamond and graphite.

3 Only exothermic reactions can be made to occur readily.

The Ans is D

Imagine a reaction which requires heat input of 10,000 kJ, to break the bond of the reactants. Then, as energy is produced when the bonds of the products are formed, let's say 9998kJ was formed. What's the overall enthalpy? +2kJ. It might seem at first that the reaction is easy to perform, but in fact, the activation energy is very high.
Therefore, statement 1 is correct.
Statement 2 is obviously wrong. (Btw this allows you to choose D immediately)
Statement 3 is not true. Some endothermic reactions can be rapid as well. Dissolving sugar is not that hard is it? It's endothermic.

 

[Metanoia]

For this question, the correct answer is B. However, I got the answer A...
My working steps are:
K2O+H2O->2KOH
2KOH+H2SO4->K2SO4+2H2O
Found the no of moles for H2SO4, which is 0.03 mol, then used mole ratio and got the no of moles for KOH, which is 0.06 mol
I then used mole ratio and found no of moles for K2O, 0.03 moles
Mass of K2O=o.o3 mol X Mr K2O
=2.83 .....

http://postimg.org/image/vd4jealez/

You missed out on the dilution factor. Only 25cm3 out of the 250cm3 KOH was used for neutralization.

 

[princess Anu]

Option 2 is incorrect. Sulfuric acid can act as an acid because the oxygen atom in ethanol has two lone pairs, either of which can accept the proton.

Oh yeah I thought It said it does behave as an acid..
Though even if it said that & the statement was that H2So4 behaves as an acid in ethanol.. wud that be correct here? Is it related to the theory? :s If yes, is it because, as you mentioned, oxygen in ethanol accepting the proton??

 

[Mathemagical]

Oh yeah I thought It said it does behave as an acid..
Though even if it said that & the statement was that H2So4 behaves as an acid in ethanol.. wud that be correct here? Is it related to the theory? :s If yes, is it because, as you mentioned, oxygen in ethanol accepting the proton??

Yes, H2SO4 can behave as an acid because it can donate a proton to ethanol.

 

[shazmina]

Imagine a reaction which requires heat input of 10,000 kJ, to break the bond of the reactants. Then, as energy is produced when the bonds of the products are formed, let's say 9998kJ was formed. What's the overall enthalpy? +2kJ. It might seem at first that the reaction is easy to perform, but in fact, the activation energy is very high.
Therefore, statement 1 is correct.
Statement 2 is obviously wrong. (Btw this allows you to choose D immediately)
Statement 3 is not true. Some endothermic reactions can be rapid as well. Dissolving sugar is not that hard is it? It's endothermic.

Great explanation, thank you sooo much

 

[nehaoscar]

It's complicated. http://www.chemguide.co.uk/basicorg/isomerism/ez.html#top

Oh i thought for cis-trans you have to have 2 same components on the 2 carbon chains
But with E-Z you can have different ones!
Okay Thankyou!

 

[nehaoscar]

How to do??

 

[nehaoscar]

why is 2 wrong?
More H+ concentration = more acidic ... so why is it wrong?

 

[nehaoscar]

Why does decomposition temperature increase?

 

[nehaoscar]

How to do??

 

[The Godfather]

How to do??

Try to balance the number of electrons in both the equation then when u cancel out, you will see 1:2 ratio..

 

[nehaoscar]

Try to balance the number of electrons in both the equation then when u cancel out, you will see 1:2 ratio..

Oh so you just always balance the electrons?
Thankyou!

 

[The Godfather]

How to do??

no of moles of oxygen = 0.0125 mol
no of moles of calcium = 0.0287 mol
no of moles of magnesium = 0.0473 mol
no of moles of potassium = 0.0294 mol
no of moles of sodium = 0.0500 mol
Answer is sodium so considering its equation, you can check other.
4Na + O2 ---> 2Na2O
To check the no of moles,
1mol of O2 = 4mol of Na
So, no of mole of sodium = 0.0125 * 4 = 0.05mol
OR
no of moles of Oxygen = 0.005/4 = 0.0125mol