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    • Thread Starter
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    Hiya I'm really not liking these pH equations at the moment. Could someone please tell me how you know when to use which one or any useful tips on them. For example how would you find the H+ conc of CH3COOH with a pH of 5.6. Thanks
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    use the basic equation

    pH = -log[H+] in a rearranged form which makes [H+] the subject
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    As the above user says, you just need to use that formula.
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    Ohhh I over complicated that in my head. What I'm really stuck on is these Ka ones, do you only ever use this equation on weak acids? And when your adding a strong acid to water what formula would you use to find the ph/conc of that solution? Sorry I'm pretty confused
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    the calculation of pH for strong and weak acids are different - all pure acids are molecular in nature - when they dissolve in water they split up into ions - strong acids dissociate completely so for strong monoprotic acids such as HCl the concentration of the acid gives the conc of H+(aq) directly however weak acids (the majority of acids) dissociate only to a small extent so the equilibrium law must be used to determine the conc of H+(aq) i.e. Ka
 
 
 
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