Edexcel CHEMISTRY DOUBTS!!!!

[Vampire-Love4ever]

A2:

Why does addition of water make the reaction between  Ammonium chloride and Sodium nitrate (lll) become spontaneous?

[wakemeup]

A2:

Why does addition of water make the reaction between  Ammonium chloride and Sodium nitrate (lll) become spontaneous?

First we have to ask ourselves that what does spontaneous mean? It means the tendency of the reaction 'to go'. In other words, an increase in entropy and therefore, the number of ways of distributing energy. When we introduce a liquid such as water between 2 solids, the disorder and randomness of the energy distributed when the reaction takes place also increases. So when the reaction does happen, energy can be more easily distributed among the products and therefore, the reaction is spontaneous.

[Vampire-Love4ever]

First we have to ask ourselves that what does spontaneous mean? It means the tendency of the reaction 'to go'. In other words, an increase in entropy and therefore, the number of ways of distributing energy. When we introduce a liquid such as water between 2 solids, the disorder and randomness of the energy distributed when the reaction takes place also increases. So when the reaction does happen, energy can be more easily distributed among the products and therefore, the reaction is spontaneous.

Thank you!

My brain doesn't seem to working a.t.m.

[sharleen07]

Um in the manufacture of paracetamol, in the last step we add ethanoic anhydride or ethanoyl chloride to 4-aminophenol. The amino group only reacts..why doesnt the -OH group react? Shouldnt it react with ethanoyl chloride to give ester?

I have another question..what is the peak area ratio for 2-methylpropanal?

[Romeesa-Chan]

Unit 6B, Sample Paper, Q3f.

Could some one please explain it?

[Romeesa-Chan]

Unit 6B, Jan 2011, Q1d.

Please explain how to do that question.

[wakemeup]

Unit 6B, Sample Paper, Q3f.

Could some one please explain it?

As the solution is diluted more than 250 cm³, the amount of Fe²⁺ ions in each portion of 25cm³ decreases which means that the volume of Potassium manganate required for each titration is less as well.

Unit 6B, Jan 2011, Q1d.

Please explain how to do that question.

We know that the potassium ions are present and that Chromium ions are present as well. We know that the only anion is the sulphate ion so the only possibility is that both cations form a salt with the anion and therefore K₂SO₄.Cr₂(SO₄)₃ is the answer.

[Romeesa-Chan]

As the solution is diluted more than 250 cm³, the amount of Fe²⁺ ions in each portion of 25cm³ decreases which means that the volume of Potassium manganate required for each titration is less as well.


We know that the potassium ions are present and that Chromium ions are present as well. We know that the only anion is the sulphate ion so the only possibility is that both cations form a salt with the anion and therefore K₂SO₄.Cr₂(SO₄)₃ is the answer.

But, how do we make the formula of the complex? 

[wakemeup]

But, how do we make the formula of the complex? 

That's a rather simple technique. When two ions combine, charges are interchanged into the number of the atoms present . Like in this question, Potassium ion has a +1 charge, so there is one sulphate. The sulphate ion has a -2 charge, so there are 2 Potassiums in the formula. Similarly, Chromium ion has a +3 charge, so there are 3 sulphates and 2 Chromiums in the formula.


Hope that helps

[Romeesa-Chan]

That's a rather simple technique. When two ions combine, charges are interchanged into the number of the atoms present . Like in this question, Potassium ion has a +1 charge, so there is one sulphate. The sulphate ion has a -2 charge, so there are 2 Potassiums in the formula. Similarly, Chromium ion has a +3 charge, so there are 3 sulphates and 2 Chromiums in the formula.


Hope that helps

THANKS ALOT! Your explanation was great! Thanks sooooo much!!!!!!!!!!!!!

[wakemeup]

You're welcome.

[Romeesa-Chan]

Jan 2011, Q 2 a ii & iii

Please explain it. =)

[elemis]

Jan 2011, Q 2 a ii & iii

Please explain it. =)

Could you link the paper or attach it , please.

[Romeesa-Chan]

Could you link the paper or attach it , please.

[Romeesa-Chan]

No one? =/