Check out Is “Much” Singular or Plural? by rogersgeorge. Here is an excerpt:
We think of “much” as a measure of part of a group of things, so it has a plural feel to it, but it’s a singular! (The equivalent plural is “many.”) So we ask, “How much is enough?” But take a look at this sentence, taken from Bruce Schneier’s book on cyber security, Click Here to Kill…
The full article is available here.