Edexcel CHEMISTRY DOUBTS!!!!

[Banana]

^ Righton! 

But just to be more clear...find the moles of Mg(OH)2 first...then muultiply by 2 to find moles of OH1-

Then you find the conc. of OH1-= n/v

Find the H+ conc by dividing the Kw by the OH1- conc...

pH= -loh H+...as Amelia said 

I'm too lazy to do the calculations 

[Blizz_rb93]

A Student prepared a sample of the fertilizer ammonium sulfate by adding ammonia solution to sulfuric acid:
2NH3 (aq) + H2SO4 (aq) --> (NH4)2SO4 (aq)

a) Calculate the theoretical maximum  yield that can be obtained by reacting 25.0cm3 of 2.0mol dm-3 ammonia solution with an excess of sulfuric acid

can someone help me figure this out? I dont know what to do i tried finding amount of NH3 by amount of substance in solution = volume x conc. and then finding its mass then using mole ratio to find mass of sulfuric acid but i always got wrong answer can someone explain the method?

thank you

[The Golden Girl =D]

Thanks guys ..sorry for NOT replying last night .. thanks again =]

[Amelia]

Most welcome, GG. 

A Student prepared a sample of the fertilizer ammonium sulfate by adding ammonia solution to sulfuric acid:
2NH3 (aq) + H2SO4 (aq) --> (NH4)2SO4 (aq)

a) Calculate the theoretical maximum  yield that can be obtained by reacting 25.0cm3 of 2.0mol dm-3 ammonia solution with an excess of sulfuric acid

can someone help me figure this out? I dont know what to do i tried finding amount of NH3 by amount of substance in solution = volume x conc. and then finding its mass then using mole ratio to find mass of sulfuric acid but i always got wrong answer can someone explain the method?

thank you

"From the equation:
2mol NH3 will produce 1 mol (NH4)2SO4

Mol NH3 in 25.0cm³ of 2.0M NH3 = 25/1000*2 = 0.05 mol NH3
This will produce 0.05/2 = 0.025 mol (NH4)2SO4
Molar mass (NH4)2SO4 = 132.14 g/mol
0.025mol = 0.025*132.14 = 3.30g (NH4)2SO4"

Allright?

[Blizz_rb93]

Most welcome, GG.  

"From the equation:
2mol NH3 will produce 1 mol (NH4)2SO4

Mol NH3 in 25.0cm³ of 2.0M NH3 = 25/1000*2 = 0.05 mol NH3
This will produce 0.05/2 = 0.025 mol (NH4)2SO4
Molar mass (NH4)2SO4 = 132.14 g/mol
0.025mol = 0.025*132.14 = 3.30g (NH4)2SO4"

Allright?

ohh okay i get it now thank you!

[The Golden Girl =D]

Can someone Explain to me how blood acts as a Buffer.   It's a research (i've just to explain it that's all) I have to do for chem.

This is what I wrote , I don't even know if it's right  

How does Blood act as a Buffer Solution?

Carbon dioxide (CO2) is a gaseous waste product from metabolism. The blood carries carbon dioxide to the lungs, where it is exhaled. More than 90% of carbon dioxide in the blood exists in the form of bicarbonate (HCO3) [which is a buffer found in blood plasma] . The rest of the carbon dioxide is either dissolved carbon dioxide gas (CO2) or carbonic acid (HCO3). The kidneys and lungs balance the levels of carbon dioxide, bicarbonate, and carbonic acid in the blood.

Carbon dioxide is mainly transported as (H2CO3) in the blood.  It dissociates as follows:
 H2CO3   HCO3? + H+

Since there will be more H+   available in the Blood , the pH will decrease .

 
Blood has to be kept at pH 7.4.  

It is buffered using Carbonic Acid [H2CO3].

Reference:

http://www.webmd.com/a-to-z-guides/bicarbonate

^ it's incomplete as you can see    

thanks =]

[Amelia]

^ Explaining all that in clearer words.

Oxidation of glucose in the body for energy release.
C₆H₁₂O₆+60₂---> 6CO₂+6H₂0

Your blood is now left with a waste disposal problem, which is potentially poisonous. The problem and part of the solution, lies in the equation below. The rates of both forward and backward reactions in the equilibrium is rapid, thanks to the enzyme carbonic anhydrase.

H₂O+CO₂<--->H⁺ + HCO₃^-

The generation of H⁺ ions if unchecked, would lead to a lowering of blood pH and you would slip into a coma. Your blood needs a buffer.

There are three buffers in the blood.
1) HCO₃^- (hydrogencarbonate ions, the most important ones.
2) Haemoglobin
3) Plasma proteins.

Hydrogen ions in the blood are "mopped" up by hydrogen bicarbonate ions, the equation (above) in which the equilibrium is well to the left. The Co2 produced is carried to the lungs and breathed out.

[The Golden Girl =D]

Here is what I wrote copied off

[~ Miss Relina ~]

why  modern methods based on mass spectroscopic measurements of carbon isotope ratios are now used intead of carbon dating anylinks plz 

[Romeesa-Chan]

why  modern methods based on mass spectroscopic measurements of carbon isotope ratios are now used intead of carbon dating anylinks plz 

It is more accurate.

[~ Miss Relina ~]

It is more accurate.

Thanks for contributing this is good one  

but they need a kind of research and I searched but nothing found yet if u plz do have anything else post it I would be very thankful  

[Romeesa-Chan]

Thanks for contributing this is good one  

but they need a kind of research and I searched but nothing found yet if u plz do have anything else post it I would be very thankful  

Welcome. (:

I tried doing a research on it as well but kinda failed at that. =/ Sorry.

[~ Miss Relina ~]

Welcome. (:

I tried doing a research on it as well but kinda failed at that. =/ Sorry.

no probs   

[The Golden Girl =D]

Q. 47] d)ii) => Attached

it's done like this ;

[CO₂] = 0.126 * 0.0224

[CO₂]= 2.82*10^-3

Part in RED : is what I got from part d)i)

I don't get why it's done that way  

I need this by tomorrow [would appreciate it if you did it for me ]


Thanks =]

[~ Miss Relina ~]

Q. 47] d)ii) => Attached

it's done like this ;

[CO₂] = 0.126 * 0.0224

[CO₂]= 2.82*10^-3

Part in RED : is what I got from part d)i)

I don't get why it's done that way  

I need this by tomorrow [would appreciate it if you did it for me ]


Thanks =]

well I copied that form answers just to clarify it

hope that u get it or even understand that messy handwriting