Question

What color would hydrochloric acid ($pH = 1$) turn into a universal indicator?
A.) Orange
B.) Purple
C.) Yellow
D.) Red

Answer 1

Hint: Universal indicator is a solution of many indicators which shows different color changes for solutions with different $pH$values. For a highly acidic solution or low $pH < 3$, it will turn red.

Complete step by step answer:
In this question, the universal indicator is a mixture of many indicators which gives different colors at different $pH$ values of the entire scale. We use universal indicators to measure the strength of an acid or a base. To know whether the given solution is a weak or strong acid or base, we first put a drop of the solution to be tested on a strip of universal indicator paper. Then, this universal indicator paper produces a new color which is used to find the $pH$ value of the given solution by matching the color with the colors on the $pH$ color chart.
The solution having $pH$ less than $3$ gives red, $pH(3 - 6)$gives orange or red color,$pH = 7$ gives green color, $pH(8 - 5)$ gives blue color and $pH( > 11)$ gives indigo color.
The $pH$ color chart in which at different $pH$ the universal indicator shows different colors can be shown as:

$pH$	Color
$0$	Dark red
$1$	Red
$2$	Red
$3$	Orange red
$4$	Orange
$5$	Orange yellow
$6$	Greenish yellow
$7$	Green
$8$	Greenish blue
$9$	Blue
$10$	Navy blue
$11$	Purple
$12$	Dark purple
$13$	Violet
$14$	Violet

As we can see , hydrochloric acid ($pH = 1$) will turn the universal indicator red.

Hence, option D is the correct answer .

Note:
Remember that for acidic solution, universal indicator shows red for strong acid, orange for medium acid and yellow for weak acid. Also, it shows green color for a neutral solution . It shows blue for weak base, purple for medium base and violet for highly basic solution.