1) A cannon after firing recoils due to Force exerted by cannon ball on the cannon.
2) Magnesium ribbon on burning produces an ash. The color of the ash is bright white.
3) Na₂ SO₄ (aqua) + Ba Cl₂ (aqua) → 2 Na Cl (solid) + Ba SO₄ (solid). Insoluble Barium Sulfate precipitate is formed
4) Akash observed an onion peel under the microscope. The peel was stained, and it appeared pink. The stain used is iodine.