'À laquelle' confusion

Question

I get really confused with knowing when to use expressions such as "à laquelle". I've read the lesson however for this text for example, why can't I use "que" as well as "à laquelle" for - 'une surprise à laquelle je ne m'attendais pas du tout' ?

Accepted Answer

The phrase is: s'attendre à qqc. So you couldn't say une surprise que je m'attendais, because que is the direct object and you need an indirect object. You cannot say ...à qui je m'attendais because that's only on option for animals and persons. Your only option is to use ... à laquelle je m'attendais.
 À + qui, auquel, à laquelle = to whom, what, which (relative pronouns)