Answer:
B
Explanation:
H2 + Cl2 → 2HCl
Hmm redox reaction.
Energy is needed to break the bonds of H-H in H2 and Cl-Cl in Cl2
Answer:
17
Explanation:
the atomic mass is away protons + neutrons, electrons are neglatable.
The last one 1) exothermic; 2) exothermic
Answer: Volume of the gas at STP is 22.53 L.
Explanation:
Given : Volume = 125 mL (as 1 mL = 0.001 L) = 0.125 L
Temperature = 
Pressure = 
According to the ideal gas equation, the volume of given nitrogen gas is calculated as follows.
PV = nRT
where,
P = pressure
V = volume
n = number of moles
R = gas constant = 0.0821 L atm/mol K
T = temperature
Substitute the values into above formula as follows.

Hence, volume of the gas at STP is 22.53 L.