Density of nitrogen= 1.20 g/l
no. of grams of nitrogen=m= (1.20g/l)(15.0l)= 18 g
molar mass of nitrogen=M= (14*2)= 28 g/mol
no. of moles of nitrogen=m/M=18/28= 0.643 moles
0.1 M x 0.5L = 0.05 mols HCl.
Adding 25 mL 2M NaOH is
2M x 0.025 L = 0.05 mols NaOH.
What you want to do is to back off very slightly with the NaOH (you might try something like 24.95 mL which I calculate to give 0.00019 M or a pH of 3.7. Inching closer, 24.99 mL would leave H^+ of 4E-5 for pH 4.4. The problem here is two-fold.
hope it helps
A physical exothermic process
A mixture of sand and table salt can be separated by filtration because the substances in the mixture differ in solubility. Because sand and table salt have a different ability to dissolve they can easily be separated. What can be done to separate this mixture is to add water to it and stir it thoroughly. The salt will easily dissolve in water while the sand will stay insoluble. The filtration of this mixture will result in salt being drained off with water while only the sand will remain.
