Question

For the reaction `2Na + 2H_2O -> NaOH + H_2`, how many grams of hydrogen are produced from 130 g of sodium?

Answer 1

Well how many moles of sodium metal do you have......?

Explanation:

`"Moles of sodium"=(130*g)/(22.99*g*mol^-1)=5.65*mol.`

Now you have the stoichiometric equation:

`2Na(s) + 2H_2O(l) rarr 2NaOH(aq) + H_2(g)uarr`

If there are `5.65*mol` of metal, clearly `(5.65*mol)/2` dihydrogen gas are evolved......, i.e. `2.83*mol` `H_2`. Typically, in a question like this, you would also be asked to calculate the volume the gas occupies under standard conditions, and the `pH` of the resultant solution (would it be high, low, neutral?).

Just as an aside, I would not want to be the mug who placed such a quantity of sodium metal in water. The reaction would be violent and explosive.