. Which among the following statement(s) is(are) true? Exposure of
silver chloride to sunlight for a long duration turns grey due to
(i) the formation of silver by decomposition of silver chloride
(ii) sublimation of silver chloride
(iii) decomposition of chlorine gas from silver chloride
(iv) oxidation of silver chloride
(a) (i) only (b) (i) and (iii)
(c) (ii) and (iii) (d) (iv) only
Which among the following is(are) double displacement reaction(s)?
(i) Pb + CuCl2 → PbCl2 + Cu
(ii) Na2SO4 + BaCl2 → BaSO4 + 2NaCl
(iii) C + O2 → CO2
(iv) CH4 + 2O2 → CO2 + 2H2O
(a) (i) and (iv) (b) (ii) only (c) (i) and (ii) (d) (iii) and (iv)
A dilute ferrous sulphate solution was gradually added to the beaker containing acidified permanganate solution. The light purple colour of the solution fades and finally disappears.
Which of the following is the correct explanation for the observation?
(a) KMnO4 is an oxidising agent, it oxidises FeSO4
(b) FeSO4 acts as an oxidising agent and oxidises KMnO4
(c) The colour disappears due to dilution; no reaction is involved
(d) KMnO4 is an unstable compound and decomposes in presence of FeSO4 to a colourless compound.
Three beakers labelled as A, B and C each containing 25 mL of water were taken. A small amount of NaOH, anhydrous
CuSO4 and NaCl were added to the beakers A, B and C respectively. It was observed that there was an increase in
the temperature of the solutions contained in beakers A and B, whereas in case of beaker C, the temperature of the
solution falls. Which one of the following statement(s) is(are) correct?
(i) In beakers A and B, exothermic process has occurred.
(ii) In beakers A and B, endothermic process has occurred.
(iii) In beaker C exothermic process has occurred.
(iv) In beaker C endothermic process has occurred.
(a) (i) only (b) (ii) only (c) (i) and (iv) (d) (ii) and (iii)
Which of the following are exothermic processes?
(i) Reaction of water with quick lime
(ii) Dilution of an acid
(iii) Evaporation of water
(iv) Sublimation of camphor (crystals)
(a) (i) and (ii) (b) (ii) and (iii) (c) (i) and (iv) (d) (iii) and (iv)
Which of the following statements about the given reaction are correct?
3Fe(s) + 4H2O(g) → Fe3O4(s) + 4H2(g)
(i) Iron metal is getting oxidised
(ii) Water is getting reduced
(iii) Water is acting as reducing agent
(iv) Water is acting as oxidising agent
(a) (i), (ii) and (iii) (b) (iii) and (iv) (c) (i), (ii) and (iv) (d) (ii) and (iv)
The following reaction is an example of a
4NH3(g) + 5O2(g) → 4NO(g) + 6H2O(g)
(i) displacement reaction
(ii) combination reaction
(iii) redox reaction
(iv) neutralisation reaction
(a) (i) and (iv) (b) (ii) and (iii) (c) (i) and (iii) (d) (iii) and (iv)
Which of the following is not a physical change?
(a) Boiling of water to give water vapour
(b) Melting of ice to give water
(c) Dissolution of salt in water
(d) Combustion of Liquefied Petroleum Gas (LPG)
Explain the role of decomposers in an ecosystem. Why are they important for maintaining balance in nature?
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