Br gen chem section 5 q22 on equivalence

[Dragongirl]

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Hello!,

The q is, 1 gram of which acid requires 30 ml of .2m naoh to reach equivalence?

The answer choice gives the mw of the weak acid. My question is since it's a weak acid/strong base titration, only half the mole equivalence of the strong base is needed to reach equivalence so wouldn't the acid need to have twice the moles as naoh does (.012 moles)?

Br states that only half equivalence of the acid is needed? Is that a mistake or am I wrong?

 

[Like]

If I understand correctly, you want to neutralize the acid with the base. You have 0.006 moles of NaOH and would need the same amount of a monoprotic acid.

 

[Dragongirl]

I'll rewrite the whole question in TBR so it becomes clearer. " 1.0 gram of which acid requires exactly 30 ml of .2M NaOH to reach equivalence?

A. Acetic acid MW = 60
B. p nitro benzoin acid MW = 167

Both acids are weak and monoprotic. I realized my mistake. At equivalence, equal moles of the acid and base certainly react to become neutralized. It's only in making a buffer that half the mole equivalent of the strong base NaOH is needed to react with the weak acid. Thanks 🙂

 

[Like]

Exactly, your answer is B. 😛 And you're very welcome.