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Subjects

Science

Chemical Reactions and Equations

रासायनिक अभिक्रियाएँ और समीकरण

In Class 10 Science, under the chapter Chemical Substances – Nature and Behaviour, this topic introduces chemical reactions as changes that form new substances. Students learn to identify reactants and products, represent reactions through word and chemical equations, and write balanced equations using correct chemical formulae while following the law of conservation of mass.

Practice questions

What is the real purpose of adding a small amount of acid during electrolysis of water?Why does a reddish-brown coating form on an iron nail and the solution turn green when the nail is placed in copper sulphate solution?What is the microscopic reason for fading of blue colour of copper sulphate solution?In the reaction \(\mathrm{CuO + H_2 \rightarrow Cu + H_2O}\), which reactant is the reducing agent?Two aqueous solutions are mixed and a white insoluble solid and sodium chloride are formed. What could be the original solutions?Which of the following equations represents a displacement reaction in which oxidation and reduction occur simultaneously?Which statement correctly describes oxidation and reduction in the reaction \\(\mathrm{CuO + H_2 \rightarrow Cu + H_2O}\\)?When copper(II) oxide is heated with hydrogen, copper is formed. Which process occurs to copper(II) oxide in this reaction?In which of the following reactions does the same element undergo both oxidation and reduction simultaneously?If substance A loses oxygen and substance B gains that oxygen, what is the correct sequence of changes in substances A and B?In the reaction (2 ext{Al}+3 ext{CuCl}_2 ightarrow2 ext{AlCl}_3+3 ext{Cu}), a student says that 1 mol of aluminium will produce 1 mol of copper. Which statement correctly corrects the error?Which of the following reaction is an example of an exothermic displacement reaction?Which environment is most favourable for rusting of iron?A student places a clean zinc strip in a blue copper sulphate solution. After some time, a reddish-brown coating forms on the strip and the blue colour of the solution fades. Which is the correct explanation of this observation?Why can iron remain protected from rusting for some time even if the zinc coating in galvanisation is scratched?What is the main chemical process behind bad taste and smell of oils and fats?A student heated copper powder in air. The reddish-brown copper turned black. Which statement about this change is correct?In a nitrogen-filled packet, how are the oils in chips mainly prevented from becoming rancid?Which statement is correct for the reaction \\(CuO + H_2 \rightarrow Cu + H_2O\\)?A student wrote the thermal decomposition of lead nitrate as Pb(NO₃)₂ → PbO + NO₂ + O₂ and claimed that it was balanced. Which change gives the correct balanced equation?