1) (a) Colorless
(b) Yellow
(c) Blue
(d) Red
2) Dip litmus paper into each test tube. The one that turns red contains the acid, the one that turns blue contains the base, and the one with no color change contains water. Litmus turns red in acidic solutions, blue in basic solutions, and remains unchanged in neutral solutions like water.
3) Na₂ZnO₂ (Sodium zincate)
4) Phenolphthalein — it remains colorless in acidic solutions and turns pink in basic solutions.
5) Activity: Place sodium carbonate in a test tube and add dilute hydrochloric acid. Bubble the gas produced through lime water. Observation: Lime water turns milky, confirming CO₂.
Equation: Na₂CO₃ + 2HCl → 2NaCl + H₂O + CO₂↑
6) Hydrogen gas (H₂). Example: Add zinc to dilute sulfuric acid; collect the gas and bring a burning splint near it — a ‘pop’ sound confirms hydrogen.
7) Concentrated sulfuric acid does not react with sodium chloride under normal conditions because it is non-volatile and does not displace volatile HCl easily without heating. Also, concentrated H₂SO₄ may dehydrate or oxidize rather than act as a typical acid. No gas (HCl) is produced at room temperature, so litmus shows no reaction.
8) A = Mg(OH)₂, B = H₂O; C = H₂SO₄, D = H₂O
Reactions:
Mg(OH)₂ + 2HCl → MgCl₂ + 2H₂O
H₂SO₄ + K₂O → K₂SO₄ + H₂O
9) Methanoic acid (Formic acid)
Parent Tip: Review the logic above to help your child master the concept of acids bases and salts worksheet answers.
