What’s given in the problem
A solution turns red litmus paper blue.
Helpful information
Acids turn blue litmus paper red.
Bases turn red litmus paper blue.
The pH scale ranges from 0 to 14, with values below 7 being acidic and values above 7 being basic.
A pH of 7 is neutral.
How to solve
Determine if the solution is acidic or basic, then use the pH scale to find the likely pH.
1. Step 1
Determine if the solution is acidic or basic
Since the solution turns red litmus paper blue, it is basic in nature.
2. Step 2
Determine the likely pH
A basic solution has a pH greater than 7.
Among the options given, only 10 is greater than 7.
Solution
The pH of the solution is likely to be 10.