Chemistry
Give one example each that illustrates the following characteristics of a chemical reaction:
(a) evolution of a gas
(b) change of colour
(c) change in state
Chemical Reaction
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Answer
(a) In many chemical reactions one of the product is a gas.
When zinc reacts with dilute sulphuric acid, hydrogen gas is evolved with an effervescence.
Zn + H2SO4 (dil) ⟶ ZnSO4 + H2 (g)
(b) Certain chemical reactions are characterised by a change in the colour of the reactants.
When a few pieces of iron are dropped into a blue coloured copper sulphate solution, the blue colour of the solution fades and turns into light green.
Fe + CuSO4 (aq) ⟶ FeSO4 + Cu
(c) In many chemical reactions a change of state is observed.
Ammonia and hydrogen chloride gases react to produce a white solid of ammonium chloride.
NH3 (g) + HCl (g) ⟶ NH4Cl (s)
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Related Questions
(a) Define a chemical reaction.
(b) What happens during a chemical reaction?
(c) What do you understand by a chemical bond?
How do the following help in bringing about a chemical change? Explain each with a suitable example.
(a) Pressure
(b) Light
(c) Catalyst
(d) Heat
(a) Define catalyst.
(b) What are (i) positive catalysts and (ii) negative catalysts? Support your answer with one example for each of them.
(c) Name three biochemical catalysts found in the human body.
What do you observe when dilute sulphuric acid is added to granulated zinc?