The number of moles of Kr present is 4.75 × 10⁻³ moles. The correct option is a. 4.75 × 10⁻³ moles
Stoichiometry
From the question, we are to determine the number of moles Kr present in 398 mg Kr.
From the formula,
[tex]Number \ of \ moles = \frac{Mass}{Atomic\ mass}[/tex]
Mass of Kr = 398 mg = 0.398 g
Atomic mass = 83.798 g/mol
Number of moles = [tex]\frac{0.398}{83.798}[/tex]
Number of moles = 0.0047495 mole
Number of moles ≅ 4.75 × 10⁻³ moles
Hence, the number of moles of Kr present is 4.75 × 10⁻³ moles. The correct option is a. 4.75 × 10⁻³ moles
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