Answer:
3.71 x10^23 molecules (corrected to 3 significant figures).
Explanation:
Take the atomic mass of N=14.0067; O = 15.999
no. of moles = mass / molar mass
no. of moles of N2O5 = 66.5 / (14.0067x2 + 15.999x5)
= 0.61569 mol
no. of molecules= no. of moles x Avogadro's constant (6.022 × 10^23 mol-1)
Therefore,
no. of molescules= 0.61569 x 6.022 × 10^23
=3.71 x10^23 molecules (corrected to 3 significant figures).
