Question 1
What is the relationship for finding the amount of substance in moles?
The right answer is the one marked above.
n = m ÷ M. That is, amount of substance = mass ÷ molar mass.
Writing it as n = M ÷ m is the common slip. Checking that the answer must be below 1 when the mass is less than the molar mass catches an inverted division at once.