Question

How many molecules of zinc oxide are there in a 2 kg (2,000 g) sample?

Answer 1

1.48 x 10²⁵ molecules ZnO

Step-by-step explanation:

To find the amount of molecules, you need to (1) convert grams to moles (via molar mass) and then (2) convert moles to molecules (via Avogadro's Number). It is important to arrange the conversions/ratios in a way that allows for the cancellation of units.

Molar Mass (ZnO): 65.380 g/mol + 15.998 g/mol

Molar Mass (ZnO): 81.378 g/mol

Avogadro's Number:

6.022 x 10²³ molecules = 1 mole

2,000 g ZnO 1 mole 6.022 x 10²³ molecules
--------------------- x ----------------- x --------------------------------------- =
81.378 g 1 mole

= 1.48 x 10²⁵ molecules ZnO