Some say ignorance is bliss.
In general yes. For example, if you accuse someone of ignorance it definitely has negative connotations. I only use the term when I refer to my own field of knowledge.
There is not specific collective noun for the noun ignorance. The noun ignorance is an uncountable noun; quantities of ignorance are expressed in degrees, for example, some ignorance, much ignorance, total ignorance, etc. A term that expresses ignorance as a collective would be, 'the collective ignorance of a group' or 'the combined ignorance of a group'.
a lack of knowlegde in my English classs
Stacy felt really ignorance when her mom left her alone in the guest room.
No, it is not an example of irony. Irony typically involves a contrast between what is expected and what actually happens. In this case, asking for the definition of ignorance is a straightforward request for information.
Ignorance leads to more ignorance. Example, ignorant people hire ignorant people, because they do know better. Ignorant people do not know that there is some thing better. Ignorant people do not look for smarter ways to do things and to learn more.
His failure to follow simple instructions was not a misunderstanding but simply the result of plain ignorance. After answering the question wrong, Celia's ignorance of mathematics was painfully obvious.
Cannons, rifles, and ignorance.
Their ignorance of the English language was bewildering.
Hammurabi
Appeal to Ignorance
Invention of scripting and painting revolutionized Ignorance. it is one of the example.