In a titration of hno3, you add a few drops of phenolphthalein indicator to 50.00 ml of acid in a flask. you quickly add 20.00 ml of 0.210 m naoh but overshoot the end point, and the solution turns deep pink. instead of starting over, you add 30.00 ml of the acid, and the solution turns colorless. then, it takes 7.23 ml of the naoh to reach the end point. what is the concentration of the hno3 solution

The HNO3 solution has a concentration of 0.07 M

Explanation:

Step 1: find a balanced equation

HNO3 (aq) + NaOH (aq) → NaNO3 (aq) + H2O (l)

⇒ for 1 mole of HNO3 reacted, there will also react 1 mole of NaOH, and be produced 1 mole of NaNO3 and 1 mole of H2O, since the ratio is 1:1

Step 2: Calculating moles

Since we know that for 1 mole of HNO3 there will react 1 mole of NaOH, we can calculate the number of moleNaOH

⇒ Concentration = mole / volume

⇒ 0.210 = mole / ((20 + 7.23 ml) *10^-3)

mole = 0.005733 mole NaOH  = 0.005733 mole HNO3

Step 3: Calculating the concentration of HNO3

Concentration = mole / volume

C(HNO3) = 0.005733 mole / ((50 + 30 ml) *10^-3)

C(HNO3) = 0.07 M

The HNO3 solution has a concentration of 0.07 M

To control this we can calculate through the following formule:

0.02723L x 0.21 M x ( 1mol HNO3 / 1 mol NaOH) x (1/ 0.08L) = 0.07M

it means there are 3 atoms of oxygen