Why does a acidic solution contains some OH ions

Measuring which physical property is most likely to produce the most precise results when trying to identify a substance

How many moles of cu are needed to react with 5.8 moles of agno3? cu + 2 agno3 → cu(no3)2 + 2 ag

What is the mass of naoh that would have to be added to 500 ml of a solution of 0.20 m acetic acid in order to achieve a ph of 5.0?