How many molecules are present in 1.75 moles of dihydrogen monoxide

The main knowledge you'd have to know to answer this question is the Avogadro's number. It is an empirical data which represents the number of molecules per mole of any substance. It is equal to 6.022*10²³ molecules/mole.

Number of molecules = 1.75 moles*6.022*10²³ molecules/mole = 1.054*10²⁴ molecules