Chemistry: Post your doubts here!

[bubbles1997]

Hi All! Please help us in tomorrow's chemistry practical.
Feel free to post anything related.
https://www.xtremepapers.com/community/threads/as-chemistry-2015-m-j.41585/

 

[phanttasy]

i have problem while solving question number b iii)
your help will be much appreciated

 

[Mathemagical]

answer given is B.. can someone explain why 2 is correct? View attachment 54350

Option 2 is correct because it takes less energy for HI to dissociate into H2 and I2 so there is a greater proportion of these gases in the equilibrium. Hence, the value of Kp is smaller.

 

[princess Anu]

how do we get these ratios?

 

[The Sarcastic Retard]

how do we get these ratios?

Is D the answer?

 

[princess Anu]

It's B

Is D the answer?[/QUOTE}

 

[The Sarcastic Retard]

i have problem while solving question number b iii)
your help will be much appreciated

25 ---> 2*10^-3
250 --> ?

 

[The Sarcastic Retard]

It's B

Oh sorry, I meant B. Visual error.
Well here is how you do that,
2NaCl(aq) + 2H2O(l) -------------> 2Na+(aq) + 2OH-(aq) + Cl2(g) + H2(g)
NaOH : 2
H2 : 1
Cl : 1

 

[fantastic girl]

Just wanna say again I'm not sure but:
If aluminium hydroxide and barium hydroxide are being formed by reaction with water it's probably got to do with OH- ions from water forming dative bond with the metal atoms...
So if there is more such OH- ions in the mixture, there would probably be a higher rate of occurance for this bond formation... Due to random movement and collision and bla bla the high concentration of the OH- increases reaction rate. I suppose. I hope someone else has a more thorough answer.

Wow that's a gud thinking xD
I didn't go so deep xP
Thank you so much =)

 

[princess Anu]

Oh sorry, I meant B. Visual error.
Well here is how you do that,
2NaCl(aq) + 2H2O(l) -------------> 2Na+(aq) + 2OH-(aq) + Cl2(g) + H2(g)
NaOH : 2
H2 : 1
Cl : 1

How did u come up with this overall equation? can u post the method of obtaining the overall equation

 

[princess Anu]

I am not getting the ans.. can someone try?

 

[The Sarcastic Retard]

How did u come up with this overall equation? can u post the method of obtaining the overall equation

Half equation method.
http://www.gcsescience.com/pt11.htm

 

[The Sarcastic Retard]

I am not getting the ans.. can someone try?

moles:
n of O2 ---> 0.0125 mol
n of Ca ---> 0.028 mol
n of Mg --> 0.047 mol
n of K ----> 0.029 mol
n of Na ---> 0.05 mol

Reactions:
2Ca + O2 ---> 2CaO
2Mg + O2 --> 2MgO
4Na + O2 ---> 2Na2O
4K + O2 ---> 4K2O

From the number of moles calculated, see which one of it satisfies with these equations.

Doing it for option (D) 0.0125 * 4 = 0.05.

 

[princess Anu]

Half equation method.
http://www.gcsescience.com/pt11.htm

the link mentions the initial anode cathode equations only ..I wanted to know how to arrive at this equation...'' 2NaCl(aq) + 2H2O(l) -------------> 2Na+(aq) + 2OH-(aq) + Cl2(g) + H2(g)''

 

[phanttasy]

25 ---> 2*10^-3
250 --> ?

Thank you very much

 

[The Sarcastic Retard]

the link mentions the initial anode cathode equations only ..I wanted to know how to arrive at this equation...'' 2NaCl(aq) + 2H2O(l) -------------> 2Na+(aq) + 2OH-(aq) + Cl2(g) + H2(g)''

God knows.

 

[Metanoia]

How did u come up with this overall equation? can u post the method of obtaining the overall equation

There is no need to do the half equations if you are unsure. Clues are already provided in the question stem.

Reactants: NaCl and H2O
Products: NaOH, H2 and Cl2

NaCl + H2O --> NaOH + H2 + Cl2

Alls thats left to do is to balance the equation.

 

[The Sarcastic Retard]

There is no need to do the half equations if you are unsure. Clues are already provided in the question stem.

Reactants: NaCl and H2O
Products: NaOH, H2 and Cl2

NaCl + H2O --> NaOH + H2 + Cl2

Alls thats left to do is to balance the equation.

Hell ya :/

 

[phanttasy]

Whats is the oxidation of S in CS2? The answer says —2 but i calculated myself i got +1

 

[Autumn98]

It's probably A, strong acid + strong base = highest enthalpy, weak acid + strong base = lower enthalpy and so on.

Oh... thankyou