Question

In the reaction `H_2(g) + F_2(g) ->2HF(g)`, how many grams of `HF` gas are produced as 5 mol of fluorine react with excess `H_2`?

Answer 1

100

Explanation:

Normally 1 mole of `F_2` reacts with 1 mole of `H_2` giving 2 moles of HF (which is 20g).

We can say that 1 mole of `F_2` gives 20 g of `HF`.
The questions is: 5 moles of `F_2` give x (how much `HF`?)

`1 - 20`
`5 - x`
`x = 100 g`