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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

Which of the following reactions is a decomposition reaction but not a thermal decomposition reaction?Which arrangement is most suitable for reliably testing the law of conservation of mass?An iron nail is kept in a blue copper sulphate solution for some time. A reddish-brown coating forms on the nail and the solution turns light green. Which statement about this change is correct?When calcium carbonate is heated in an intact closed container, it decomposes into calcium oxide and carbon dioxide. If the carbon dioxide does not escape, what can be concluded about the total mass of the container and its contents before and after the reaction?During a reaction in an open container, if a produced gas escapes, why can the measured mass of the container and its remaining contents appear to decrease?What is the main reason for keeping atoms of every element equal on both sides of a balanced equation?Why is it incorrect to change the subscripts in a chemical formula while balancing a chemical equation?How many hydrogen atoms are present in two water molecules?In the balanced equation \(2Mg + O_2 \rightarrow 2MgO\), what is the total number of oxygen atoms on the product side?What is the main purpose of rubbing magnesium ribbon with sandpaper before burning it?Which substance is the white powder formed when a magnesium ribbon burns in air?When water is added to calcium oxide, one product forms and heat is released. What is the correct combined identification?Which solid product is formed when calcium carbonate is strongly heated?The gas produced on heating calcium carbonate turns lime water milky. Which gas is it?The appearance of brown gas on heating lead nitrate identifies which gas?What is the solid residue in the thermal decomposition of lead nitrate?Why is it incorrect to identify the brown gas evolved on heating lead nitrate as oxygen?Why does silver chloride turn grey in sunlight?What is the main reason for storing silver bromide in a dark-coloured bottle?What is the volume ratio of hydrogen gas to oxygen gas produced during the electrolysis of water?