Answer: The coefficient in front of AgCl when the equation is properly balanced is 2.
Explanation:
According to the law of conservation of mass, mass can neither be created nor be destroyed. Thus the mass of products has to be equal to the mass of reactants. The number of atoms of each element has to be same on reactant and product side. Thus chemical equations are balanced.
Decomposition is a type of chemical reaction in which one reactant gives two or more than two products.
Decomposition of silver chloride is represented as:

Thus the coefficient in front of AgCl when the equation is properly balanced is 2.
Answer:
2H2 + O2 -----> 2H2O
Not sure about the second question though.
Answer:
7.5 pounds per square-inch
At sea level, one square-inch of any surface has about 15 pounds of air sitting on top of it. At 18,000 feet, that same square inch has only 7.5 pounds per square-inch (psi) exerted on it.
The reaction is
Cu⁺²(aq) ---> Cu(s) [reduction]
The species which undergoes reduction is able to oxidize other one thus will called as "oxidizing agent"
Thus Cu⁺² is an oxidizing agent
or Cu is a reducing agent
Al(s) ---> Al⁺³(aq)
Aluminium is undergoing oxidation
Thus is able to reduced others and hence is a reducing agent
Al is a reducing agent
or Al⁺³ is an oxidizing agent
Answer: Cu is the reducing agent, and AI3+ is the oxidizing agent.