A karmelit (such as a sea or covered walkway) is treated as which domain for impurity purposes?
Halacha 2: a karmelit is treated as a public domain for impurity — doubt about impurity there is ruled pure.
Question 2
The entire Temple Courtyard (azarah) — is it public or private domain for impurity?
Halacha 3: the entire azarah (Temple Courtyard) is treated as a public domain for impurity — doubt about impurity there is pure.
Question 3
A container 10 handbreadths high sits in the public domain with impurity inside. A person inserts his hand INTO the container. Doubt whether he touched the impurity. Is he impure?
Halacha 11 (halacha 10): the exterior of a tall container is public domain (doubt = pure); but inserting one's hand inside creates a private-domain situation — the interior of the container is private-domain space.
Question 4
A store is open to the public domain. Someone enters the store but is unsure if he entered the impure store or the pure one (of two adjacent stores). Is he impure?
Halacha 9 (halacha 8): a store is a private domain. Doubt about entering an impure store vs. a pure store = private-domain doubt = impure. (Entering just one impure store in public domain would be pure.)
Question 5
A zav was riding on his donkey. Another person was also riding nearby. Doubt whether they touched. Is the second person impure?
Halacha 13 (last halacha): in all the cases listed at the end of the chapter — including a zav and another person both riding in the public domain — the doubt is pure.