pH and indicators
2 marks · EasyA student tests two solutions with litmus paper. Solution X turns blue litmus red. Solution Y turns red litmus blue. How many solutions are acidic?
Work this out on paper, then compare with the answer and worked solution below. With a free account you can submit written answers for marking.
Show answer
1 (±0)
Common mistakes: counting both if they only look at change
Show mark scheme and worked solution
Marking points
M1 · 1 mark · Identifies that blue to red indicates acid and red to blue indicates alkali
A1 · 1 mark · Correctly states 1 solution is acidic
Worked solution
Solution X turns blue litmus red — this indicates an acid. Solution Y turns red litmus blue — this indicates an alkali.
So, only one solution is acidic.