A12.8 g sample of naoh contains how many molecules?

To determine the number of molecules present for a given mass of a substance, we need to convert it from units of mass to moles by using the molar mass. Then, we use Avogadro's number to convert it to moles. We do as follows:

12.8 g NaOH (1 mol NaOH / 40 g NaOH) ( 6.022 x10^23 molecules NaOH / 1 mol NaOH) = 1.927x10^23 molecules NaOH present

Cooking soup does not induce a phase change in the water as it is still water. Melting is an endothermic reaction in that it draws in heat which also applies to the frost disappearing. Freezing is an exothermic reaction in that it gives off energy in order to make what being frozen colder which satisfies answer A.