Answer:
Solid oxalic acid - color of the blue litmus paper does not change. It is blue.
Solid oxalic acid + water - color of the blue litmus paper changes. It became red.
Explanation:
Because no free H+ - ions in solid oxalic acid, the blue litmus paper will not change color. It will stay blue.
Solid oxalic acid + water - free H+ - ions is formed, color of the blue litmus paper changes. It became red.
