Questions! (1 Viewer)

[Premus]

hey

just a few questions...

1. HPO4 2- is an amphiprotic species.
name a second chemical species which together with this ion can form a buffer solution in water. briefly explain the buffering action in this example.

i know a buffer is made up of a weak acid and its conjugate base. the conjugate base here is PO4 3- ...... but how do u go abt writing equations for it to act like a buffer??


2. Explain why a low level of dissolved oxygen might be related to :
a) turbidity
b) temperature ?

Thanks

 

[Paroissien]

HPO42- + H2O <---> PO43- + H3O+
That's what I'd say, but that is just an educated guess.

Hmm, well I guess low level of DO might lead to the death of organic matter, thus meaning there is more crap just sitting in the water. ??
And temperature... I can't think of anything. My guess is it would drop

 

[Xayma]

1.
La Chateliers principle it forms an equilibrium process.

With an acid

H₃O_(aq)⁺+PO_4(aq)^3- <----> H₂O_(l)+HPO_3(aq)^2-

reverse effect for a base

2. Turbidity I think is one sign of stagnation indicating there is no stirring of particle.

O_2(g)<---->O_2(aq) &Delta;H=-ve

&there4; as temperature increases (decreases) solubility and hence amount of oxygen in the water decreases (increases)

 

[d_elmo]

well i did HCO3- in the blood, just show how it could act as both an acid and a base in order to adjust the pH in the system if needed.

the eqn's would look like this:


HCO3- + H2O <--> H2CO3 + OH-
(this is the hydrogen carbonate acting as a base)

HCO3- + H2O <--> CO3 2- + H3O+
(this is the hydrogen carbonate acting as an acid)



low levels of DO would occur in very turbid/murky water as the lack of light prevents plants in the water from undergoing photosynthesis and hence the production of oxygen is reduced. i dunno about temp though, soz.

hope i helped ya

 

[tina_goes_doo]

What Xayma said about the temperature is correct. With an increase in temperature there is a decrease in gas solubility. Think about boiling water or that experiment you did in heating soft drink.

And for the buffer:

HPO4 2- + H2O <---> H2PO4 - + OH-

H2PO4 - + H2O <---> HPO4 2- + H3O

This buffer controls the pH by shifting the above equilibriums in the appropriate directions.

In acid was present, HPO4 2- would accept H+ increase the pH of the solution.

If a base was present, H2PO4 - would produce H+ to lower the pH of the solution.

 

[Paroissien]

So therefore your second chemical species is H2PO4- right?

 

[Xayma]

It could be either.

H₂PO₄^-+2H₂O <------> HPO₄^2-+H₃O⁺+H₂O <------> PO₄^3-+2H₃O⁺

Is an extended buffer.