Molecules of SiO2 would have a mass of 12.40 g

1.244x10^23 molecules

Explanation:

From Avogadro's hypothesis, 1mole of any substance contains 6.02x10^23 molecules.

This means that 1mole of SiO2 contains 6.02x10^23 molecules

1mole of SiO2 = 28 + (2x16) =28 +32 = 60g

If 1 mole(i.e 60) of SiO2 contains 6.02x10^23 molecules,

Therefore, 12.40g of SiO2 will contain = (12.40 x 6.02x10^23) / 60 = 1.244x10^23 molecules

chemical digestion occurs in the stomach were hcl and pepsin forms chyme, the mouth in which salivary amylase breaks down starch to form bolus, and the small intestine specifically the duodenum.