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

(i), (ii), (iii)

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(i), (ii), (iv)

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(ii), (iii), (iv)

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(i), (ii), (iii), (iv)

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Solution

The correct option is D
(i), (ii), (iii), (iv)

If you were observing only the changes without knowing the underlying reaction, all four of the given events may be chemical reactions because:
(i) Colour change occurs
(ii) Change of state has happened from gas to solid
(iii) Change in temperature has occurred
(iv) A gas has been released

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Similar questions

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. Which of the following are chemical changes ?
(i) decaying of wood
(ii) burning of wood
(iii) sawing of wood
(iv) hammering of nail into wood

(a) (i) and (ii)
(b) (ii) and (iii)
(c) (iii) and (iv)
(d) (i) and (iv)

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

Q. Classify the following as physical and chemical changes:
(i) Cleaning with soap and water
(ii) Cooking chicken
(iii) Formation of clouds
(iv) Making ice candy

A) Physical change - (i), (ii), (iii); chemical change - (iv)

B) Physical change - (i), (iii), (iv); chemical change - (ii)

C) Physical change - (i), (ii); chemical change - (iii), (iv)

D) Physical change - (i), (iii); chemical change - (ii), (iv)

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