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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 correct reason for considering photosynthesis a chemical reaction?Why is it wrong to change subscripts while balancing an equation?How does a balanced equation show conservation of mass?What is done to balance a skeletal chemical equation?If a reaction container feels cold to the touch during a chemical reaction, what is the most appropriate conclusion?If the container becomes hot during a reaction, which conclusion is most suitable?If bubbles form during an experiment, what is the most careful conclusion?What is the correct meaning of an upward arrow in a chemical equation?What is the correct meaning of a downward arrow in a chemical equation?When is the aqueous symbol used?When an iron nail is placed in a blue copper sulphate solution, the solution changes colour and copper gets deposited. What type of reaction is this?Which of the following is a decomposition reaction but not a photolytic decomposition reaction?A student writes the reaction of steam with red-hot iron as \(Fe + H_2O \to FeO + H_2\). Which option correctly corrects the error?A student dipped an iron nail in a blue copper sulphate solution for some time. A reddish-brown coating formed on the nail and the solution turned green. Which type of reaction does this change illustrate?What is the most reliable indication that a chemical reaction has occurred?In a closed container, the total mass remains the same before and after a chemical reaction. Which law does this illustrate?When two aqueous solutions are mixed and a white solid insoluble in water is formed, which type of reaction does this indicate?If, during a change, the colour changes, a gas is formed, and heat is released, what is the most appropriate conclusion?In a closed container, the total mass of the reactants is 50 g. Until the reaction is complete, no matter leaves the container and no matter enters it. What will be the total mass of the products?In the equation \(2\mathrm{H}_2 + \mathrm{O}_2 \rightarrow ?\) for the formation of water, how many water molecules will be present on the product side?