chemistry question!!?

K

koolaid

New member
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 0.0502 M NaOH but overshoot the end point, and the solution turns deep pink. Instead of starting over, you add 33.50 mL of the acid, and the solution turns colorless. Then, it takes 3.08 mL of the NaOH to reach the end point.

(a) What is the concentration of the HNO3 solution?


(b) How many moles of NaOH were in excess after the first addition?
 
Total up the volumes of HNO3 and NaOH, then do the math...

HNO3(aq) + NaOH(aq) --> NaNO3(aq) + HOH(l)
83.5 mL ..... 23.08 mL
..? M ..........0.0502M

Find the moles of NaOH. There will be the same moles of HNO3. Moles over liters will give the molarity of the acid.

0.02308 L x (0.0502 mol NaOH / L) x (1 mol HNO3 / 1 mol NaOH) x ( 1/ 0.0835 L) = 0.0139 M HNO3
 
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