A chemist reacted 0.05 moles of sodium with water to form 50cm3 of sodium hydroxide solution.

Na + H2O -- NaOH + H2 (unbalanced)
What mass of sodium was reacted?

2 answers

2Na + 2H2O -- 2NaOH + H2

mols Na = grams Na/atomic mass Na.
You know atomic mass Na and mols Na, solve for grams Na. The 50 cc NaOH has nothing to do with the problem assuming that the water used was in excess.
4cc