When do you use ask and request?
The verbs ask and request are close in meaning, but there are important differences in their use, as your question suggests. Let's start with their meanings.
The two main meanings of ask are
1) To request a response to a question, as in these examples:
2) To request something more than just an answer, such as directions, food, or help, as in these examples:
The meaning of request is similar to the second meaning of ask above. In fact, request can be substituted for ask/ask for in many of the example sentences shown for this meaning of ask, as shown in the two sentences below.
However, request does not share the first meaning of ask shown above: to request a response to a question.
It's important to be aware that, in addition to this difference in meaning,request is a much more formal and polite word than ask, and it is used less often. It is more common to use ask, except in formal and formulaic language, such as the examples below:
I hope this helps.