Question

$20ml$ of $0.5N$ $HCl$ and 35 mL of $0.1N$ $NaOH$ are mixed. The resulting solution will:

• A. be neutral
• B. be basic
• C. turn phenophthalein solution pink
• D. turn methyl orange red

Answer 1

The correct option is D turn methyl orange red

20 mL of 0.5 N $HCl$ $=\frac{20mL}{1000mL/L}\times 0.5geq/L=0.01geq$ $HCl$.

35 mL of 0.1 N NaOH $=\frac{35mL}{1000mL/L}\times 0.1geq/L=0.0035geq$ $NaOH$.

0.0035 g eq of $NaOH$ will neutralise 0.0035 g eq of $HCl$.

However 0.01 g eq of $HCl$ are present. Hence, $HCl$ is excess

reagent.

Hence the resulting solution will be acidic.

It will turn methyl orange red or pink.

Note: in acidic solution, methyl orange indicator has red colour.