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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 distinction between the symbols  ext{(aq)} and  ext{(l)} in a chemical equation?In an unknown process, a new substance was formed, the colour changed, and the total mass remained the same in a closed container. What is the most appropriate conclusion?In a closed container a metal reacts with acid and gas forms but does not escape. What is the most suitable conclusion about total mass?Why is measuring less mass after gas escapes from an open container not against conservation of mass?While balancing a chemical equation, the number of atoms of each element is kept the same on the reactant and product sides. Which law does this demonstrate?Why is it safer to change coefficients rather than subscripts when balancing a chemical equation?If the number of atoms of any one element is not the same on the reactant and product sides of a chemical equation, what is the equation called?What is the total number of atoms in two water molecules?What will be the ratio of magnesium atoms to oxygen atoms in three units of magnesium oxide?Why does removing the layer formed on the surface of a magnesium ribbon make its burning clearer?Why can burning of magnesium be considered both combination and oxidation?What is the correct name of the product formed when water is added to calcium oxide?Why is the reaction between calcium oxide and water called an exothermic combination reaction?In the reaction \(\mathrm{CuO + H_2 \rightarrow Cu + H_2O}\), which of the following statement is correct?During the thermal decomposition of calcium carbonate, the evolved gas is passed through lime water, which turns milky. This confirms the presence of which gas?Which pair correctly identifies the brown gas and the colourless gas formed when lead nitrate is heated?Which substance is the yellow solid residue formed on thermal decomposition of lead nitrate?On heating lead nitrate, brown fumes indicate the presence of which gas?A student places a zinc strip in a blue copper sulphate solution and says that the blue colour fades because copper is more reactive than zinc. Which correction to this statement is correct?When white silver chloride g( gCl) is exposed to sunlight, it turns grey. Which product is responsible for this colour change?