25.0 mL portions of the following 0.100 M solutions are titrated with 0.100 M HCl. Which statements are correct?

AFor $Na X_{2} CO X_{3}$ , the phenolphthalein end point is at 25.0 mL
BFor $Na X_{2} CO X_{3}$ , the methyl orange end point is at 75.0 mL (total)
CFor $NaHCO X_{3}$ , the methyl orange end point is at 25.0 mL
DFor a 25.0 mL solution that is 0.100 M in both NaOH and $Na X_{2} CO X_{3}$ , the phenolphthalein end point is at 50.0 mL

Answer: A, C, D

Na X_{2} CO X_{3}

: 2.50 mmol, first stage needs 2.50 mmol HCl = 25.0 mL (true), total to

CO X_{2}

= 5.00 mmol = 50.0 mL, not 75.0 mL (false).

NaHCO X_{3}

: 2.50 mmol needs 25.0 mL (true). NaOH +

Na X_{2} CO X_{3}

: phenolphthalein stage = 2.50 + 2.50 = 5.00 mmol = 50.0 mL (true).