Chemistry · Class 10 CBSE
A student burns a magnesium ribbon in air and observes a bright white flame along with the formation of a white powder. Which statement correctly explains this reaction?
While performing an experiment, a student notices bubbles forming when zinc granules are added to dilute hydrochloric acid. The bubbles are due to the evolution of:
A piece of iron is left in the open during the rainy season. After a few weeks, a reddish-brown coating appears. Which condition is essential for this change?
Which observation is the strongest evidence that a chemical reaction has taken place?
A student writes the following equation: H₂ + O₂ → H₂O Why is this equation incorrect?
A silver ornament becomes black after being kept unused for several months. Which process is responsible?
A farmer adds quicklime (CaO) to water before using it in the field. The container becomes hot. Which type of reaction is taking place?
A student passes electricity through acidified water and observes gases being collected at both electrodes. Which type of reaction is taking place?
Copper powder is heated in air, forming black copper oxide. Hydrogen gas is then passed over the black substance, and the brown colour of copper reappears. Which statement is correct?
A student mixes sodium sulphate solution with barium chloride solution. A white insoluble solid forms immediately. This reaction is best classified as:
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A student burns a magnesium ribbon before and after cleaning it with sandpaper. Why is the ribbon cleaned before burning? Explain.
2 marksDifferentiate between oxidation and reduction using one suitable example.
2 marksWhy is balancing a chemical equation important? State any two reasons.
2 marksGive one example each of: - A combination reaction - A decomposition reaction Explain why they belong to their respective categories.
2 marksA shopkeeper paints iron gates regularly. Explain how painting helps prevent corrosion.
2 marksClassify the following reactions and justify your answer: 1. CaO + H₂O → Ca(OH)₂ 2. 2AgCl → 2Ag + Cl₂ (sunlight) 3. Fe + CuSO₄ → FeSO₄ + Cu 4. Na₂SO₄ + BaCl₂ → BaSO₄ + 2NaCl 5. CH₄ + 2O₂ → CO₂ + 2H₂O
5 marksExplain the process of corrosion. In your answer, include: - Definition of corrosion - Conditions required for rusting - Two methods of preventing corrosion - Economic importance of preventing corrosion
5 marksCase study: Rahul performed an experiment in the laboratory. He added iron nails to a blue copper sulphate solution and left the beaker undisturbed for 30 minutes. He noticed that the blue colour of the solution gradually faded, and a reddish-brown coating appeared on the iron nails. Answer the following questions: (a) Name the type of chemical reaction taking place.
1 markCase study: Rahul performed an experiment in the laboratory. He added iron nails to a blue copper sulphate solution and left the beaker undisturbed for 30 minutes. He noticed that the blue colour of the solution gradually faded, and a reddish-brown coating appeared on the iron nails. Answer the following questions: (b) Why did the colour of the solution change?
1 markCase study: Rahul performed an experiment in the laboratory. He added iron nails to a blue copper sulphate solution and left the beaker undisturbed for 30 minutes. He noticed that the blue colour of the solution gradually faded, and a reddish-brown coating appeared on the iron nails. Answer the following questions: (c) Write the balanced chemical equation for the reaction.
1 markCase study: Rahul performed an experiment in the laboratory. He added iron nails to a blue copper sulphate solution and left the beaker undisturbed for 30 minutes. He noticed that the blue colour of the solution gradually faded, and a reddish-brown coating appeared on the iron nails. Answer the following questions: (d) Why is iron able to displace copper from copper sulphate solution?
1 mark