Answer:
Ag+
Explanation:
If you imagine as if the problem were double replacement, you would pair the Cl with one of the following ions provided in the choices. As seen on Table F, Ag+ paired with Cl- produces an insoluble compound, hence the precipitate. All the other ions shown in the multiple choice section, when paired with Cl- will produce a soluble compound, as a result NOT a precipitate.
Answer: The reaction is exothermic
The
value is negative.
Heat is a product.
Explanation:

Endothermic reactions are defined as the reactions in which energy of the product is greater than the energy of the reactants. The total energy is absorbed in the form of heat and
for the reaction comes out to be positive.
Exothermic reactions are defined as the reactions in which energy of the product is lesser than the energy of the reactants. The total energy is released in the form of heat and
for the reaction comes out to be negative.
The substances which are written on the left side of the arrow are reactants and the substances which are written on the right side of the arrow are products. Thus heat is a product.
Answer:
a. the 3 represents the principal energy level
Explanation:
3 is the principal energy level. The p is the sublevel. 4 is the possible occupying electron.