Observing the changes, in which of the following would you say a chemical reaction may be occurring?

Heating iodine changes its colour from bluish black to purple

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Mixing ammonia and hydrogen chloride gases gives fumes containing a white powdery substance

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Mixing an acid and a base solution raises the temperature

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Mixing ferrous sulphide and hydrochloric acid gives off a gas with a rotten egg smell

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Solution

The correct options are
A Heating iodine changes its colour from bluish black to purple
B Mixing ammonia and hydrogen chloride gases gives fumes containing a white powdery substance
C Mixing an acid and a base solution raises the temperature
D Mixing ferrous sulphide and hydrochloric acid gives off a gas with a rotten egg smell
The given processes involve:
(i) colour change
(ii) change of state
(iii) change in temperature
(iv) release of a gas

These are the characteristics of a chemical reaction. Therefore, all four of the given processes may be chemical reactions.

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Similar questions

Q. Observing the changes, in which of the following would you say a chemical reaction may be occurring?
(i) Heating iodine changes the colour from bluish black to purple.
(ii) Mixing ammonia and hydrogen chloride gases gives fumes containing a white powdery substance.
(iii) Mixing an acid and a base solution raises the temperature.
(iv) Mixing ferrous sulphide and hydrochloric acid gives off a gas with a rotten egg smell.

By observing the mentioned events below, which of the following shows chemical change?
(i) Heating iodine changes the colour from bluish black to purple
(ii) Mixing ammonia and hydrogen chloride gases gives fumes containing a white powdery substance
(iii) Mixing an acid and a base solution raises the temperature.
(iv) Mixing ferrous sulphide and hydrochloric acid gives off a gas with a rotten egg smell

Name the following:
(i) Acid present in the stomach of mammals.
(ii) Drying agent used to dry hydrogen chloride.
(iii) Salt obtained by heating sodium chloride with concentrated sulphuric acid below 200 degree celsius.
(iv) Gas that yields dense white fumes when mixed with hydrogen chloride.
(v) Two solution that yield white precipitates, when treated with hydrogen chloride or hydrochloric acid.
(vi) Gas obtained by treating metals with hydrochloric acid.
(vii) Gas obtained by treating ferrous sulphide with hydrochloric acid.
(viii) Five oxidizing agents that liberate chlorine from concentrated hydrochloric acid.
(ix) Acid used to extract glue from bones.
(x) A chloride which is soluble in excess of ammonium hydroxide.
(xi) A greenish yellow gas.
(xii) A chemical in which gold can be dissolved.
(xiii) A metallic oxide which reacts with hydrochloric acid to give a coloured solution.
(xiv) Two colourless gases which when mixed produce a white solid.

Q. A greenish yellow gas burns in a rotten egg smelling gas giving an acidic gas and a yellow coloured non metal. Write the balanced chemical equation of the reaction.

Write the balanced chemical equations for the following reactions-

(a) Sodium carbonate on reaction with hydrochloric acid in equal molar concentration gives sodium chloride and sodium hydrogen carbonate.

(b) Sodium hydrogen carbonate on reaction with hydrochloric acid gives sodium chloride, water and liberates carbon dioxide.

(c) Copper sulphate on treatment with potassium iodide precipitates cuprous iodide $({Cu}_{2} I_{2})$ , liberates iodine gas and also forms potassium sulphate.

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