Answer:
1.126 x 10^22
Explanation:
pV = nRT
7.53 x 10 = n x 8.31 x 485
n = (7.53 x 10) / (8.31 x 485) = 0.0187 moles
M = n x Avogadros number
0.0187 x 6.02 x 10^23 = 1.126 x 10^22
Answer:

Explanation:
Half time is period required to desintegrating the half of the initial number of atoms. Then, the total time is:


Answer: Option (a) is the correct answer.
Explanation:
A decomposition reaction is defined as a reaction where a compound dissociates into two or more atoms.
For example, 
Whereas a chemical reaction in which two reactants combine together to result in the formation of a compound is known as a synthesis reaction.
For example,
is a synthesis reaction.
Thus, we can conclude that the statement chemical reaction A, because the reactant is a compound identifies the decomposition reaction and describes a substance is involved.
It will be easier to answer if you show the choices.