Chemists work with standardised solution, a solution whose concentration is known. The requirements to standardise the solution are :
1. the volume of the solution.
2. the number of moles of solute in that volume.
A primary standard solution is used in determining the molarity of a solution. To find the molarity of HCl, 0.317 g of `Na_(2)CO_(3)`, the primary standard dissolved in water, is used in titrating the solution of HCl. 22.9 mL of acid are required to neutralise the sodium carbonate. This is the needed volume (first requirement). The stoichiometric equation is used to know the second requirement.
`2HCl(aq.)+Na_(2)CO_(3)(aq.) to 2NaCl+H_(2)O+CO_(2) uarr`
The suitable indicator in the above titration will be :

Options

A. phenolphthalein
B. methyl orange
C. litmus
D. bromothymol blue

Answer

B