CBSE Class 10 Science 2018 · Paper 31(B) · Question 22

Solution A: basic (alkaline). The pH paper turns blue, a colour on the basic side of the chart, so the pH of A is more than $7$ (blue matches about pH $9$ to $10$). Solution B: acidic. The pH paper turns orange, a colour on the acidic side of the chart, so the pH of B is less than $7$ (orange matches about pH $3$ to $4$).