pH of salt solutions (1 Viewer)

[mushroom_head]

if i tested:
ammonium chloride, sodium carbonate, sodium hydrogen sulfate, distilled water, potassium nitrate, sodium phosphate and ammonium acetate.

what would be the pH of each?
i don't recall doing this prac at school~ plz help!

O yeah, and if i used a pH meter, what safety precautions do u think there are?

 

[Xayma]

Distilled Water=7
Im not entirely sure about the rest but a few are bronsted lowry acids and bases so they will partially ionise. For things like ammonium acetate Im not sure which will ionise more.

 

[xiao1985]

try to make a reasonable guess of the acid / base involved for the neutralisation ... eg, ammonium chloride will be: (ammonia + hydrocholoric acid, ie, weak base + strong acid)

use the lowry bronsted definition to find out if the ions are weak / v. weak acid or base, then determine the acidity of the salt...

just to do all of them quickly, but you should try it yourself using lowry bronsted defniition of conjugate pair to find out the acidity of the salt:

ammonium chloride(acidic)
, sodium carbonate, (basic)
sodium hydrogen sulfate, (around 7)
distilled water, (7)
potassium nitrate, (be around 7)
sodium phosphate (basic)
ammonium acetate. (hard to determind... wk acid + wk base, so around 7)

 

[~*HSC 4 life*~]

Distilled Water=7
.

at 25 deg celsius

 

[jm1234567890]

hmm... safety precautions...

since it is a probe with come KCl in it the probe itself isn't dangerous.

However, the solution you are testing could be dangerous

so lab cost, goggles, gloves, etc...

for toxic materials, mabye fume cupboard.

 

[Xayma]

at 25 deg celsius

and 101.3KPa

 

[mushroom_head]

i thought it's 100kpa now...

 

[tina_goes_doo]

at 25 deg celsius

Or 298K ^^

 

[CM_Tutor]

Xiao1985, sodium hydrogensulfate will be acidic.

All, distilled water should have a pH of 7 under SLC, but will in practice be acidic due to dissolved CO₂

 

[xiao1985]

Xiao1985, sodium hydrogensulfate will be acidic.

All, distilled water should have a pH of 7 under SLC, but will in practice be acidic due to dissolved CO₂

ohhh... is it because hydrogen sulfate anion can further ionise the water molecules to produce hydromium ions???

crab... all i looked is the strength of the original acid and base =(

 

[CM_Tutor]

ohhh... is it because hydrogen sulfate anion can further ionise the water molecules to produce hydromium ions???

Yes. The pK_a of the hydrogensulfate anion is 1.9, so a solution of 0.1 molL^-1 sodium hydrogensulfate will have a pH of around 1.45. Definitely not neutral.

 

[eth]

Please note that distilled water will have a pH of 7.0 at any temp and pressure. It does not change pH until there are impurities in it.

 

[helper]

Please note that distilled water will have a pH of 7.0 at any temp and pressure. It does not change pH until there are impurities in it.

Distilled water will normally have a pH of 6 due to the dissolved CO₂.

 

[eth]

Except for the whole if it's done properly in a vacuum, there won't be any dissolved CO2.
Granted, the stuff that's normally used has pH 6-6.5, but that's life

 

[Xayma]

Please note that post was months old.

If it is done in a vacuum it won't have any aqueous ions because it will be a gas

 

[aim54x]

If it is done in a vacuum it won't have any aqueous ions because it will be a gas

nice touch, that is one i havn't heard. very true, as the water boils off it would condense back normally. but a vaccum would spread the vapour meaning the condensation would probably not form a liquid.

buut in a closed container wouldn't the consdensation collect?? a vaccum does not affect temp.

 

[Xayma]

Boiling point is dependant on pressure.

It is Le Chateliers principle

 

[aim54x]

correct. thaty makes sense. so u can't boil the stuff in the first place, there goes that guys theory.