Question

4 observations to determine a chemical reaction took place

Answer 1

Answer:

1. change in color

2. change in temprature

3.formation of precipitate

4. evolution of gas

Answer 2

Answer:

(i) Evolution of gas: The chemical reaction between zinc and dilute H2SO4.

Zn(s)+H2SO4(aq) → ZnSO4(sq) +H2(g)↑

(ii) Change in colour: The chemical reaction between potassium iodide solution and lead nitrate solution.

Pb(NO3)2(aq)+2KI → 2KNO3(aq)+PbI2(s) Pb(NO3)2(aq)+2KI - Colourless PbI2(s)-Yellow

(iii) Formation of piecipitate : The chemical reaction between sulphuric acid barium chloride solution.

BaCl2(aq) + H2SO4(aq) → 2HCl(aq) + BaSO4(s) 2HCl(aq) + BaSO4(s)- White precipitate

(iv) Change in temperature : The ctremiial reaction between quick lime and water.

CaO(s)+H2O(l) → Ca(OH)2(aq)+Heat

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