[john_123]

 

calculate the mass of solid needed to make the solution. Explain the steps you took in making each solution and in verifying that it has the correct concentration.

12.   100 ml of solution that is 1.0 M in sodium cation, using sodium chloride.
13.   100 ml of a solution that is 0.7 M in chloride anion, using magnesium chloride (MgCl2).
14.   250 ml of a solution that is 0.34 M in sodium cation, using sodium sulfate decahydrate (Na2SO4, 10H2O).
15.   500 ml of a solution that is 0.25 M in sulfate anion, using sodium sulfate decahydrate. 


16.   You have three bottles, one filled with 1M NaAc (Sodium Acetate), one filled with 1M HAc (Acetic Acid), and one filled with distilled water. You need to create a buffer solution that has a pH of 4.75 such that when 1ml of 10M HCl is added to 100ml of your buffer, the resulting pH is 3.75 (±0.1). What concentrations of HAc and NaAc do you need to create the buffer solution?



thanks for everone help me 

[Schrödinger]

You have to show us what you have done, if you have tried to solve the problem.

[john_123]

ok!

i have some idea for some problem but i don't think it is right to answer them

first problem : i think answer is :

MgCl2 dissociates:
MgCl2 ↔ Mg 2+ + 2Cl-
1mol MgCl2 produces 2mol Cl- ions
You want a solution taht is 0.7M in Cl- ions
Therefore you must produce a 0.7/2 = 0.35M MgCl2 solution.
Moalr mass MgCl2 = 24.305+35.453+35.453 = 95.211g/mol
You want a 0.35M solution: 0.35*95.211 = 33.324g
This mass is per 1000ml of solution. You want 100ml solution. Divide by 10. This gives 3.332g MgCl2 dissolved in 100ml solution is 0.7M in Cl- ions.



^ right??

[Schrödinger]

Yup 
Now do the same for 12,14 and 15.

[john_123]

100 ml of solution that is 1.0 M in sodium cation, using sodium chloride ?

NaCl dissociates NaCl ↔  Na+(aq) + Cl-
1mol NaCl produces 1mol Na+ ions
You want a solution that is 1.0M in Na+ ions

Therefore you must produce a 1.0/1.0 = 1.0 M NaCl solution.
Moalr mass NaCl = 58.443 g/mol
You want a 1.0 M solution: 1.0*58.443 = 58.443g
This mass is per 1000ml of solution. You want 100ml solution. Divide by 10. This gives 5.844g
NaCl dissolved in 100ml solution is 1.0 M in Na+ions.
 





right ??!! ^^

[Schrödinger]

Yes that's fine. 14 and 15 are simple now, i guess.

Now try Qn. no 16.

[john_123]

Yes that's fine. 14 and 15 are simple now, i guess.

Now try Qn. no 16.

yup .. i tried 3 time before but i don't now how the way to answer it !  

and after 1 day i will do exam in bioChemistry ..  

plz again .. can you help me for this question  16!