distinguish between indirect pronouns le and la

Question

why is

'je vous la donne' the translation for 'I give it to you' when we don't know the gender of 'it'? shouldn't it be 'je vous le donne'

in the same manner why is 'je la lui a écrite' - i wrote it to her - not 'je le lui a écrit'?

Accepted Answer

Hi Julianne,
In the case of
'Je vous la donne' , 
it was in the context of 'cette carte' which is feminine and singular.
However, in -
'Je la lui ai écrite' , 
indeed we don't know what the 'la' refers to, but because it is the verb is écrire we assume that we are talking about a card or a letter,  hence the feminine singular form for 
une carte/une lettre
Hope this helps!

Answer

When you specifically use the feminine form, it is with reference to some feminine noun mentioned before in the context.

In the French sentence: Je la lui a écrite this might refer to la lettre, mentioned in a previous sentence.