Use of 'auquel' / 'à qui' instead of 'que'

Question

In the lesson ‘Que = Whom, which, that (relative pronouns)’ an example sentence is given as:
‘La femme que je dessine’

An example sentence from this lesson is: ‘Le chat, auquel tu as fait peur’ OR ‘Le chat, à qui tu as fait peur’ 
I’m struggling to understand why is ‘Le chat, que tu as fait peur’ is not used?

Thanks

Accepted Answer

Hi Stewart,
The sentence  'Le chat que tu as fait peur' is incorrect because the 'à' is missing in it.
The expression is 'faire peur à  quelqu'un' so the only pronouns you can use are 'auquel'  or 'à qui' .
In the case of 'La femme que je dessine' , the verb is 'dessiner quelque chose/ quelqu'un, so the object is direct only requiring 'que'.
Hope this helps!