You have solutions of 0.2M HNO₂ and 0.2M KNO₂. A buffer of pH 3 is needed. What volumes of HNO₂ and KNO₂ are required to make 1 liter of buffered solution?
a) 400 mL of HNO₂ and 600 mL of KNO₂
b) 600 mL of HNO₂ and 400 mL of KNO₂
c) 500 mL of HNO₂ and 500 mL of KNO₂
d) 300 mL of HNO₂ and 700 mL of KNO₂