Comparing Acids: H_2 C_2 O_4 & H_3 O^+

[danago]

Using the following reaction for example:

$$H_2 C_2 O_4 _{(aq)} + H_2 O_{(l)} \to HC_2 O_4 ^ - _{(aq)} + H_3 O^ + _{(aq)}$$

The question asks to predict weather the reaction will occur to a large or small extent. What i would usually do is decide weather the $$H_2 C_2 O_4$$ or the conjugate acid of water is a stronger acid (via a table or otherwise), and the reaction with the consumption stronger acid will be favoured.

Is there any way i can determine the relative strengths of two acids given just their chemical formula?

Thanks in advance
Dan.

 

[Gokul43201]

Look up a table of Ka or pKa values.

 

[chemisttree]

Not really. You need to look up the pKa of oxalic acid. Use the definition for pKa to determine the relative concentrations (not strengths) of H3O+ and C2H2O4.

 

[chemisttree]

Wow, Gokul's fast...

 

[danago]

Thanks for the replies :)

For some reason, we completely skipped the chapter on pKa values of acids and bases, and were told that we arent going to need to know them for our exam.

So would that mean its just a matter of knowing it? I either know it or i dont?

 

[chemisttree]

Thanks for the replies :)

For some reason, we completely skipped the chapter on pKa values of acids and bases, and were told that we arent going to need to know them for our exam.

So would that mean its just a matter of knowing it? I either know it or i dont?

Either your teacher has given you some other information that you can use to determine strength (concentration) or has overlooked how to apply pKa to the problem. Your teacher must have given you a ranking for organic acid strengths.

 

[symbolipoint]

You are probably expected to apply an inorganic molecular structure concept of acid strength. Otherwise, you have no need to merely predict - only to check Ka tables.