Answer:
1.07×10²¹ molecules are needed to sound the alarm
Explanation:
Let's convert the mass of CO to moles, to determine the amount of molecules.
0.05 g . 1 mol / 28 g = 1.78×10⁻³ moles
Now we can determine the number of molecules with the NA
1 mol has 6.02×10²³ molecules
1.78×10⁻³ moles may have (1.78×10⁻³ . 6.02×10²³) / 1 = 1.07×10²¹ molecules