For which of the following conversions does the value of the conversion factor depend upon the formula of the substance?

A) moles of any substance to number of particles

B) volume of gas (STP) to moles

C) mass of any substance to moles

D) density of gas (STP) to molar mass

The answer is: C) mass of any substance to moles.

To converte mass to amount of substances, mass must be divided by molar mass (n = m : M).

Molar mass M represent the mass of a substance divided by the amount of substance. If the formula is not correct, amount of substance is not correct.

For example, calculate molar mass of iron (II) chloride:

Atomic mass of iron is 55.8 g/mol.

Atomic mass of chlorine is 35.5 g/mol.

If compound is FeCl, molar mass would be 55,8 g/mol + 35,5 g/mol = 91,3 g/mlo, that is not correct.

If compound is FeCl₂, malar mass of compound would be:

55,8 g/mol + 2·35,5 g/mol = 126,8 g/mol, that is correct.

For which of the following conversions does the value of the conversion factor depend upon the formula of the substance?

The answer is C