Step 1: List the given values
[tex]\begin{aligned} & P = \text{0.918 atm} \\ & V = \text{2.22 L} \\ & T = 45^{\circ}\text{C} = \text{318 K} \end{aligned}[/tex]
Step 2: Calculate the number of moles of gas using ideal gas equation.
[tex]\begin{aligned} PV & = nRT \\ nRT & = PV \\ \frac{nRT}{RT} & = \frac{PV}{RT} \\ n & = \frac{PV}{\text{RT}} \\ & = \frac{(\text{0.918 atm})(\text{2.22 L})}{\left(0.0821 \: \dfrac{\text{L}\cdot\text{atm}}{\text{mol}\cdot\text{K}}\right)(\text{318 K})} \\ & = \text{0.07805943 mol} \\ & \approx \boxed{\text{0.0781 mol}} \end{aligned}[/tex]
Hence, there are 0.0781 mol of Kr in 2.22 L of the gas at 0.918 atm and 45°C.
[tex]\\[/tex]
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