Answer : The number of moles of gas present in container are 1.697 mole.
Explanation :
Using ideal gas equation,

where,
P = pressure of gas = 74 mmHg = 0.097 atm
conversion used : (1 atm = 760 mmHg)
V = volume of gas = 500.0 L
T = temperature of gas = 
n = number of moles of gas = ?
R = gas constant = 0.0821 L.atm/mole.K
Now put all the given values in the ideal gas equation, we get the number of moles of gas in the container.


Therefore, the number of moles of gas present in container are 1.697 mole.
Hi!
When titrating Calcium and Water solution, if there is some CaCO3 in the solution, the following reactions may occur in acid solution:
CaCO₃ + H⁺ → Ca⁺² + HCO₃⁻
HCO₃⁻ + H⁺ ↔ H₂CO₃ → CO₂ (g) + H₂O
The bubbles are from CO₂ that is being developed from an acidic solution of CaCO₃
That is only the combustion of a hydrocarbon. Rust is a combustion reaction because oxygen is added.
Fe(s) + O2(g) => FeO2(s)