Assuming 3.9g of the ferrous salt was dissolved in 100cm3 of distilled water, calculate it's molarity by mole concept?

a liter is 1000 cm^3 so 39 grams of this stuff

what is molar mass of this salt?
x = 56 * n + mass of whatever your salt negative stuff is
IF the salt were FeO it would be 56*1 + 16*1 = 72 grams per mol
so your answer would be
mols in 1000 cm^3 = 39 grams * 1 mol/72 grams = 39/72
HOWEVER, you did not say what salt of iron you mean

To calculate the molarity (M) using the mole concept, we need to know the molar mass of the ferrous salt and the volume of the solution.

1. Start by determining the molar mass of the ferrous salt. This can be done by looking up the atomic masses of the atoms in the compound and multiplying them by their respective subscripts. For example, if the ferrous salt is FeCl2, the molar mass would be calculated as follows:

Molar mass of FeCl2 = 1(atomic mass of Fe) + 2(atomic mass of Cl)

2. Convert the mass of the ferrous salt to moles using the molar mass determined in step 1. The formula to calculate the number of moles is:

Moles = Mass (g) / Molar mass (g/mol)

3. Determine the volume of the solution in liters. In this case, we are given the volume in cm3, so we need to convert it to liters. There are 1000 cm3 in a liter, so:

Volume (L) = Volume (cm3) / 1000

4. Calculate the molarity (M) using the number of moles from step 2 and the volume in liters from step 3. The molarity formula is:

Molarity (M) = Moles / Volume (L)

By following these steps and plugging in the appropriate values, you can calculate the molarity of the ferrous salt solution.