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The acid–base indicator methyl red has a Ka  of 1 *10–5. Its acidic form is red...

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lak-86 | Student, Undergraduate | Salutatorian

Posted August 14, 2013 at 5:21 AM via web

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The acid–base indicator methyl red has a Ka  of 1 *10–5. Its acidic form is red while its alkaline form is yellow. If methyl red is added to a colorless solution with a pH = 7, the color will be

(A)pink

(B) red

(C) orange

(D) yellow

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justaguide | College Teacher | (Level 2) Distinguished Educator

Posted August 14, 2013 at 5:49 AM (Answer #1)

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Methyl red is an indicator to differentiate acidic solutions from basic solutions. The indicator turns red in color when it is added to a solution and the pH of the solution that is being tested is less than 4.4 ;and it turns yellow in color when the pH of the solution being tested is greater than 6.2. For all pH values that lie between 4.4 and 6.2, the solution is orange in color.

When methyl red is added to a solution with a pH equal to 7, it turns orange in color. The correct answer is option C.

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