A 0.5L 1mol /LNaHCO3+0.5L 0.5mol/L NaOH
溶液内含有0.25mol5molNaHCO3和0.25molNaCO3
B 0.5L 0.75mol /LNa2CO3+0.5L 0.5mol/L HCl
溶液内含有0.25mol5molNaHCO3和0.125molNaCO3
C 0.5L 1mol/L NaHCO3+0.5L 0.25mol/L NaOH
溶液内含有0.375mol5molNaHCO3和0.125molNaCO3
D 1L 1mol/L Na2CO3+1L 0.5mol/L HCl
0.5molNaHCO3和0.5molNaCO3
所以选D