CHEM AND BIO HELP AND TIPS HERE

[nid404]

to ur 1st question

The heat given out would be distributed in a larger volume of acid....so temp rise will be less...
H=mcdt  (h=heat given out/absorbed, c=sp heat capacity, dt=change in temp)
H will be the same
m will increase.....c is constant....so dt will decrease

ya?

[nid404]

Another example.

 
If 50 cm3 of HCl 1 mol/dm3 conc. are added to 1 g of CaCO3. We get a max. CO2 volume of 60 cm3

 If 50 cm3 of HCl 0.5 mol/dm3 conc. are added to 1 g of CaCO3. We get a max CO2 volume of 30 cm3 BUT WHY

ok let's write down the equation

CaCO3 + 2HCl---> CaCl2 + H2O+ CO2
look at the ratio
HCl : CO2
2 :1

no of moles of HCl in case 1= 0.05---> 0.025 moles of CO2=60cm3
no of moles of HCl in case 2= 0.025--->0.0125 moles of CO2= 30cm3

got it?

[holtadit]

Got it Nid.

Thanks for taking the time out to help me... again XD


+rep

[nid404]

no prob...
I like it

[holtadit]

no prob...
I like it

Chemistry rocks....

[DEGO]

guys in MS whn it says ref. wht it means???   refer or reference???

[Dark Prince]

Hi, iwant 2 ask a few Qs

1. what is de main function of porus membrane in a membrane cell (electrolysis)
2. Is this a redox or displacement reaction....Zn + CuSO4 -- ZnSO4 +Cu  ?
3. How does afuel cell worf (hydrogen nd O2)?

[holtadit]

Hi, iwant 2 ask a few Qs

1. what is de main function of porus membrane in a membrane cell (electrolysis)
2. Is this a redox or displacement reaction....Zn + CuSO4 -- ZnSO4 +Cu  ?
3. How does afuel cell worf (hydrogen nd O2)?

1.) I think your refering to the electrolysis of conc. NaCl. The membrane allows Na+ ions to move to the right of the  cell to meet OH- ions
2.) Its both. In an exam you give any as your answer. The Zn displaces Cu from its salt at the same time losing 2 electrons to Cu2+ to form    Cu metal.
3.) ill be back...

[nid404]

guys in MS whn it says ref. wht it means???   refer or reference???

reference..

[holtadit]

Quick question:

what is the effect of pouring a strong alkali on to a metal ?

[nid404]

product would be metal hydroxide and hydrogen

not always if the metal in the alkali is more reactive, there will be no reaction

[holtadit]

Three reactions used in the manufacture of sulphuric acid are shown.

 S + O₂ -> SO₂

 2SO₂ + O₂ -> 2SO₃

 SO₃ + H2O -> H₂SO₄

Which of these reactions are redox reactions?

I dont understand how it is 1 and 2 only. Where is the reduction and oxidation going on each equation ?

[Amr Fouad]

Three reactions used in the manufacture of sulphuric acid are shown.

 S + O₂ -> SO₂

 2SO₂ + O₂ -> 2SO₃

 SO₃ + H2O -> H₂SO₄

Which of these reactions are redox reactions?

I dont understand how it is 1 and 2 only. Where is the reduction and oxidation going on each equation ?

Alright..here's the deal..First and foremost, you have to calculate the oxidation state of the Sulpher species..

1) It goes from 0 in Sulpher (natural element) to +4 i sulpher dioxide...
SO^2...X+(2x-2)=0
and so X=+4.....sulpher is oxidzed

2) It goes from +4 in sulpher dioxide (again) to +6 in sulpher trioxide..
SO^3...X+(-2x3)=0
X=+6..sulpher is oxididzed again

3) No redox reaction
It goes from +6 in sulpher trioxide to +6 in sulphuric acid...
H^2SO^4.....
The H ion is +1..and since there are 2 such ions...the sulphate ion SO^4 must have a charge of -2..

X+(4x-2)=-2
X=+6

Hope that helped..

[holtadit]

Excellent explanation. I completely understood.


+rep

[nid404]

thanks amr