How many molecules are there in 345 grams of carbon dioxide?

4.72 × 10²⁴ molecules

Explanation:

Number of mols of a substance = mass of substance/molar mass of substance

Mass of carbon dioxide (CO2) = 345g

Molar Mass of Carbon = 12

Molar Mass of Oxygen = 16

Molar mass of CO2 = 12 + (16 x 2) = 44 g/mol

Number of mols of 345 grams of CO2 = 345/44 = 7.84 mols

Number of molecules of a substance = number of mols x Avogadro's constant.

                  = 7.84 mol  x 6.02 × 10²³ /mol

                   = 4.72 × 10²⁴

Hence, the number of molecules in 345 grams of carbon dioxide is 4.72 × 10²⁴ molecules.