What is the ph of 100 ml of a buffer that is 0.5 m hcno and 0.5 m cno− when 100 ml of a 0.2 m naoh solution is added? assume the volumes are additive. ka of hcno is 3.5 × 10−4.

Given:
Buffer:
Concentration of acid = 0.5 m HCNO
Concentration of dissociated acid  = 0.5 m CNO-
Volume of buffer = 100 ml
Volume of base = 100 ml
Concentration of NaOH (base) = 0.2 m
Ka(HCNO) = 3.5x10^-4

The formula for pH buffers:

pH = pKa - log([HA]/[A-])
ph = -log(3.5x10^-4) - log(0.5)
pH = 3.76

Yes, endothermic means it turns cold. and some chemical changes include change of tempature.