Question

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Answer 1

Answer:

i. starch and iodine together causes a color change

ii. sodium + hydrochloric acid ----> sodium chloride + hydrogen

iii. iron(II) sulfate + sodium hydroxide ----> iron(II) hydroxide + sodium sulfate

Answer 2

Change In Color.

Reaction between a Zinc rod and Copper Sulphate solution.

Zinc Rod → Zn

Copper Sulphate Solution → CuSO₄

Skeletal Equation:

Zinc Rod + Copper Sulphate solution → Zinc Sulphate Solution + Copper.

Chemical Equation:

Zn + CuSO₄ → ZnSO₄ + Cu.

In this reaction, the Blue color of the Copper Sulphate [CuSO₄] solution fades away when a Zinc rod [Zn] is dipped in it, causing a change of color.

Change In Temperature.

Reaction between Quicklime/Calcium Oxide and Water.

Quicklime → CaO

Water → H₂O

Skeletal Equation:

Quicklime + Water → Calcium Hydroxide [Slaked Lime] + Heat energy

Chemical Equation:

CaO + H₂O → Ca[OH]₂ + Heat.

In this reaction, when Calcium Oxide/Quicklime [CaO] reacts with Water [H₂O], it produces Calcium Hydroxide, also known as Slaked lime [Ca[OH]₂] and relases heat, changing the temperature.

Formation of Precipitate.

Reaction between Sodium Sulphate and Barium Chloride in aqueos form.

Sodium Sulphate → Na₂So₄

Barium Chloride → BaCl₂

Skeletal Equation:

Sodium Sulphate + Barium Chloride →  Barium Sulphate + Sodium Chloride

Chemical Equation:

Na₂SO₄ + BaCl₂ → BaCl₂ + 2NaCl

In this reaction, White precipitate of Barium Sulphate is formed. Hence there is a formation of a precipate.