1.

An alkalie is titrated against an acid with methyl orange as indicator, which of the following is a correct combination

Answer»

`{:("Base","Acid","End point"),("Strong","Strong","Pinkish red to yellow"):}`
`{:("Base","Acid","End point"),("Weak","Strong","Yellow to pinkish red"):}`
`{:("Base","Acid","End point"),("Strong","Strong","Pink to colourless"):}`
`{:("Base","Acid","End point"),("Weak","Strong","Colourless to pink"):}`

Solution :`UNDERSET("weak base")(NH_(4)OH)+underset("Strong acid")(HCl) to NH_(4)Cl+H_(2)O`
At end point pH will be LESS than 7
as strong acid weak base salt have `pH=7-((pK_(b)+logc))/(2)`
`therefore`Methyl ORANGE will change colour from yellow to pinkish red at the end point.


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