a) Give one example of a chemical reaction. b) state two characteristics of the chemical reaction which takes place when dilute sulphuric acid is poured over zinc granules. c) Give two characteristics of the chemical reaction which occurs on adding potassium iodide solution to lead nitrate solution.
Answers
2Mg (s) + O2(g) 2MgO (s)
(b) When dilute sulphuric acid is poured over zinc granules, hydrogen gas is evolved and the mixture becomes hot. Hence, "evolution of a gas" and "change in temperature" are two characteristics of this chemical reaction.
Zn (s) + H2SO4 (aq) ZnSO4 (aq) + H2 (g) + HEAT
(c) On adding potassium iodide solution to lead nitrate solution, yellow precipitates of lead iodide are formed and the colour of the solution changes from colourless to yellow. Hence, "formation of a precipitate" and "change in colour" are the characteristics of this chemical reaction.
2KI (aq) + Pb(NO3)2 (aq) PbI2 (s) + 2KNO3 (aq)
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Answer:
2Mg (s) + O2(g) 2MgO (s)
(b) When dilute sulphuric acid is poured over zinc granules, hydrogen gas is evolved and the mixture becomes hot. Hence, "evolution of a gas" and "change in temperature" are two characteristics of this chemical reaction.
Zn (s) + H2SO4 (aq) ZnSO4 (aq) + H2 (g) + HEAT
(c) On adding potassium iodide solution to lead nitrate solution, yellow precipitates of lead iodide are formed and the colour of the solution changes from colourless to yellow. Hence, "formation of a precipitate" and "change in colour" are the characteristics of this chemical reaction.
2KI (aq) + Pb(NO3)2 (aq) PbI2 (s) + 2KNO3 (aq)
Explanation: