What happens if a add the following acids

[joejo]

Hey guys...Can someone please explain to me what the general affect of adding the following acids and bases to my original test on equilibrium where I had K2CrO4 and K2Cr2O7.

Observations I had made...

Solution of K2CrO4
CH3COOH becomes orange
H2SO4 becomes orange
KOH stays yellow
NH3 stays yellow
Ca(OH)2 stays yellow
C2H5OH no change

Solution of K2Cr2O7
CH3COOH stays orange
H2SO4 stays orange
KOH becomes yellow
NH3 becomes yellow
Ca(OH)2 becomes very pale
C2H5OH no change

so can someone please help explain to me what the general affect of the acids and bases are?

Also, I've noticed that Ca(OH)2 hadlittle effect on the equilibrium. Why is that?

Lastly, in what way does OH- affect the equilibrium? Does it affect it any way??

thanks again for your help!

 

[GCT]

First, write down the reaction, preferably through latex.

 

[joejo]

sorry I don't know latex...

CrO2-4 (the 4 is under the 2-) / Cr2O2- 7 (the 7 is under the 2-)

 

[whozum]

[ tex ] (CrO_4)^{2-} [ /tex ]

If you take out the gaps in the tex tags, that will give you:

$$(CrO_4)^{2-}$$

 

[GCT]

I'm referring to the whole reaction, balanced, it should have been provided to you...wasn't it?

 

[joejo]

H+ (aq) + 2CrO4 2- (aq) --><--- Cr2O72- (aq) +OH- (aq)

 

[GCT]

so can someone please help explain to me what the general affect of the acids and bases are?

Also, I've noticed that Ca(OH)2 hadlittle effect on the equilibrium. Why is that?

Lastly, in what way does OH- affect the equilibrium? Does it affect it any way??

thanks again for your help!

assuming that Cr207 is orange and Cr04 is yellow

Adding the acid shifts the equilibrium to the right, thus adding any type of arrehnius acid (one that has an acidic proton) to a solution of Cr2072- intensify the orange color; the rate of formation of Cr207 should have increased relatively since the 0H- is consumed (the reverse reaction rate has decreased relative to the forward from equilibrium where the two rates were the same). Adding a base will cause it to react with the acid concentration, the same principle applies here.

 

[joejo]

ohh yep that makes sense...thanks for u help GCT

but what is the general affect?

 

[GCT]

well it depends on what the reaction is, acids and bases are treated just like any other compound in dealing with La Chatelier's principle. Perhaps I'm not understanding you correctly.