Respuesta :

musicalscience
What you need to do is find the Molar mass of sodium and then divide your mass (0.25g) by the molar mass of Na. 

Therefore   0.25g/22.9898g/mol (do you see how the "grams" unit will cancel out? That will leave you with the number of moles you have. 

Answer: The answer is 0.011 moles. Hope this helps!