Answer : The number of moles of argon gas is, 11.5 mol
Explanation :
To calculate the moles of argon we are using ideal gas equation as:
![PV=nRT](https://img.qammunity.org/2021/formulas/physics/high-school/xmnfk8eqj9erqqq8x8idv0qbm03vnipq7i.png)
where,
P = pressure of argon gas = 658 mmHg = 0.866 atm (1 atm = 760 mmHg)
V = volume of argon gas = 30.6 L
n = number of moles of argon gas = ?
R = gas constant = 0.0821 L.atm/mol.K
T = temperature of argon gas = 28 K
Now put all the given values in the above formula, we get:
![(0.866atm)* (30.6L)=n* (0.0821 L.atm/mol.K)* (28K)](https://img.qammunity.org/2021/formulas/chemistry/middle-school/dxa6tdvabamgq70pgducue2v7zbv2nzmcw.png)
![n=11.5mol](https://img.qammunity.org/2021/formulas/chemistry/middle-school/pmw21apdoju9exe72tn4ufxa7wcsbri31g.png)
Therefore, the number of moles of argon gas is, 11.5 mol