How many grams are there in 0.250 moles of naoh?

We are asked to find the mass of 0.250 mol of NaOH
molar mass of NaOH - 40 g/mol
in other words 1 mol of NaOH has a mass of 40 g
therefore 0.250 mol of NaOH has a mass of - 40 g/mol x 0.250 mol = 10.0 g
mass of 0.250 mol of NaOH is 10.0 g

You would be correct, boiling water does disinfect contamination.    the property of disinfecting means to kill  germs, bacteria and other pathogens or contamination  that might cause an infection or cause a person to become sickly. a couple methods of disinfecting are using soap, other cleaning supplies or by simply "boiling" the contaminate.  the reason why boiling water disinfects certain attributes is because some cells cannot survive the heat and pressure.