Home › ICSE Class 8 › chemistry › Chemical Reactions › Which sequence correctly lists three indicators …
Which sequence correctly lists three indicators of a chemical change that occur together in Zn + H₂SO₄?
A{'text': 'Gas evolution, rise in temperature, no colour change'}
B{'text': 'Gas evolution, no temperature change, colour change'}
C{'text': 'Precipitate, no gas, fall in temperature'}
D{'text': 'Colour change, precipitate, no gas evolution'}
Answer & Solution
Correct answer: A. {'text': 'Gas evolution, rise in temperature, no colour change'}
1. Zn reacts with H₂SO₄ to give ZnSO₄ and H₂.
2. Visible signs: hydrogen gas bubbles out → **gas evolution**.
3. The reaction is exothermic, so the test tube becomes hot → **rise in temperature**.
4. Both Zn (grey solid) and the solution stay colourless → **no colour change**.
5. Hence the matching set is gas evolution + rise in temperature + no colour change.
_Source: Selina Concise ICSE Class 8 Chemistry Ch 6 "Chemical Reactions", Signs of chemical change_
Related questions
During photosynthesis, plants use sunlight to convert CO₂ and water into glucose. This shoIn the decomposition Pb(NO₃)₂ → PbO + 4NO₂ + O₂, the equation as written is:Why does the colour of CuSO₄ solution fade when iron filings are added?When phosphoric acid is added to hydrogen peroxide, it slows the decomposition of H₂O₂. PhWhich of the following equations represents a balanced double-displacement reaction?Which of the following pairs correctly shows an enzyme and its function inside the human bThe reaction 2H₂O → 2H₂ + O₂ in sunlight is an example of a:In the reaction Na₂CO₃ + Heat → Na₂O + CO₂, the energy requirement makes the reaction: