Answer:
The correct answer is
B.

Explanation:
Enthalpy of reaction :
It is the amount of energy released/absorbed when one mole of the substance is formed from the reactant at a constant pressure.
The enthalpy of a reaction can be calculated using :









Please note that :
The carbon monoxide , CO should be taken as C triple bond O. Not C=O .
So , the bond energy =1072 is used

Answer
Sounds travel slowest in gasses so it would be air
Explanation:
The answer is H2SO4 for sulphuric acid
Remark
The balance numbers in front of Ag and AgNO3 are both 2. That number is in moles.
Rule: if the moles are the same in the equation, then whatever you are given for one, will be the same for the other. So you have 0.854 moles of Ag. You will also have 0.854 moles of AgNO3
Answer: 0.854 <<<<<