Recall that a mole is defined as Avogadro's number of particles what the formula of caffeine basically tells us is that every molecule of caffeine you will have 8 atoms of carbon 10 atoms of hydrogen 4 atoms of nitrogen and 2 atoms of oxygen so if we have 0.3 moles of caffeine we will have 4*0.3 moles of nitrogen which is 0.12 and you got the idea
PH scale is from 1 to 14 and indicates how acidic or basic a solution is. To find pH or pOH we need to know the H⁺ ion concentration or OH⁻ concentration.
pH can be calculated using the following equation;
pH = -log[H⁺]
the H⁺ concentration of the given acid is 1.0 x 10⁻⁴ M. substituting this we can find the pH
pH = -log[1x10⁻⁴]
pH = 4
answer is 1) 4