Help with 7 and 10

6. A 25.00 mL sample of 0.150 M nitrous acid is titrated with a 0.150 M CsOH solution. What would be the equivalence point pH (K, of nitrous acid = 4.5 x 10-4)? 10.35 b. 10.65 c. 8.11 d. 7.00 7. What mass of HCI needs to be added to a 250 ml solution containing 0.500 M NaC, H,Oz X and 0.500 M HC, H,O,, to make the PH = 4.25 (K, of HC, H,O, is 1.8 x 10-5)? a. 0.237 g b. 0.563 g C. 2.35 g d. 1.45 g 8. The following K values have been measured for phosphoric acid at 298 K: K, = 7.1 x 10-3, K, = 6.3 x 10-8, and K, = 4.5 x 10-13 What is the pOH of a 0.350 M H, PO, solution? a. 0.50 b. 1.33 C. 13.15 d. 12.67 9. A titration of an acid and a base to the equivalence point results in a noticeably acidic solution. It is likely this titration is between a. A strong acid and a weak base. b. A weak acid and a strong base. c. A weak acid and a weak base (where k, equals k). d. A strong acid and a strong base. 10. Calculate the concentration of the oxalate ion (C,0 2-) in a 0.175 M solution of oxalic acid (C,H,O ) (For oxalic acid, Ka, = 6.5 x 10-2, Kaz = 6.1 x 10-5). a. 0.11 M b. 6.1 x 10-5 M 4.0 x 10-6 M d. 0.0791 M