Solution " X " contains Na ₂ CO ₃ and NaHCO ₃ . 20 ~mL of X when titrated using methyl orange indicator consumed 60 ~mL of 0.1 M HCl solution. In another experiment, 20 ~mL of X solution when titrated using phenolphthalein consumed 20 ~mL o

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Solution " X " contains Na ₂ CO ₃ and NaHCO ₃ . 20 ~mL of X when titrated using methyl orange indicator consumed 60 ~mL of 0.1 M HCl solution. In another experiment, 20 ~mL of X solution when titrated using phenolphthalein consumed 20 ~mL of 0.1 M HCl solution. The concentrations (in mol L ⁻¹ ) of Na ₂ CO ₃ and NaHCO ₃ in X are respectively

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Correct answer: B. 0.1,0.1

For titration of a basic solution of Na ₂ CO ₃ and NaHCO ₃ against HCl , if phenolphthalein is used as indicator, the end point is indicated only for half neutralization of Na ₂ CO ₃ , i.e., (upto NaHCO ₃ ). Na ₂ CO ₃+ HCl NaHCO ₃+ NaCl The remaining solution then contains the unreacted NaHCO ₃ from this reaction plus the unreacted NaHCO ₃ originally in the solution. At the phenolphthalein end point, there is no reaction between HCl and NaHCO ₃ . From the equations aligned Mol of HCl consumed & = mol of Na ₂ CO ₃ 2

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