The amount of Ferrous ascorbate equivalent to elemental iron 100 mg can be calculated by considering the molecular weights and the iron content of ferrous ascorbate.

The molecular weight of ferrous ascorbate is approximately 198.11 g/mol, and the molecular weight of elemental iron is 55.845 g/mol. Ferrous ascorbate contains 1 iron atom per molecule, so 198.11 g of ferrous ascorbate contains 55.845 g of elemental iron.

Therefore, to find the amount of ferrous ascorbate equivalent to 100 mg of elemental iron, we can set up a proportion:

```

198.11 g ferrous ascorbate / 55.845 g elemental iron = x g ferrous ascorbate / 100 mg elemental iron

```

Solving for x, we get:

```

x = (100 mg elemental iron * 198.11 g ferrous ascorbate) / 55.845 g elemental iron

x ≈ 354.48 mg ferrous ascorbate

```

Therefore, approximately 354.48 mg of ferrous ascorbate is equivalent to 100 mg of elemental iron.