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Class 10 · Science · Hard
→When an iron nail is placed in a blue copper sulphate solution, a reddish-brown copper coating forms on the nail and the solution turns pale green. What causes both changes?
Class 10 · Science · Medium
→In the electrolysis of water, if the volume of oxygen is five millilitres, what is the expected volume of hydrogen?
Class 10 · Science · Hard
→What is the main purpose of adding a few drops of dilute sulphuric acid during the electrolysis of water?
Class 10 · Science · Hard
→Which of the following equations represents an exothermic combination reaction?
Class 10 · Science · Medium
→What is the deeper reason for keeping silver bromide in a dark coloured bottle?
Class 10 · Science · Hard
→White silver chloride turns grey in sunlight. What type of reaction occurs, and which product causes the grey colour?
Class 10 · Science · Hard
→On heating lead nitrate, the evolution of a brown gas confirms the formation of which gas?
Class 10 · Science · Hard
→When lead nitrate is heated, a brown gas evolves and a solid residue remains. Which explanation is correct?
Class 10 · Science · Medium
→What is the role of heat in thermal decomposition of calcium carbonate?
Class 10 · Science · Hard
→The gas produced on heating calcium carbonate is passed through lime water. The milkiness of lime water is caused by the formation of which substance?
Class 10 · Science · Hard
→When water is added to calcium oxide, calcium hydroxide is formed and the container becomes hot. Which two types of reaction does this represent?
Class 10 · Science · Hard
→Which statement best explains the relationship between a balanced chemical equation and the law of conservation of mass?
Class 10 · Science · Hard
→In the balanced combustion reaction of magnesium, if \(2\mathrm{MgO}\) is written on the product side, how many magnesium atoms must be on the reactant side?
Class 10 · Science · Hard
→In the balanced chemical equation for the formation of water, if there are 2 water molecules on the product side, how many oxygen molecules 0( 0 ext{O}_2 0) 0 are required on the reactant side?
Class 10 · Science · Hard
→While balancing a chemical equation, if a student changes a subscript in the formula of water, \(\mathrm{H_2O}\), what mistake has been made?
Class 10 · Science · Hard
→In a closed container, 12 g of reactants completely undergo a reaction to form products, and no substance leaves the container. What will be the total mass of the products?
Class 10 · Science · Medium
→In which condition can conservation of mass be checked most correctly?
Class 10 · Science · Hard
→Which of the following observations most strongly indicates that an unknown reaction is a precipitation reaction?
Class 10 · Science · Hard
→In which of the following reactions does one part of the same reactant undergo oxidation while another part undergoes reduction?
Class 10 · Science · Medium
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