Chemical Reactions — Set 3
Chemistry · रासायनिक अभिक्रियाएं · Questions 21–30 of 40
Which metal is used for galvanizing iron to protect it from rusting?
Correct Answer: D. Zinc
Zinc provides a protective coating that prevents oxygen and moisture from reaching the iron. Even if the coating is scratched, zinc corrodes preferentially to protect the iron. This process is a common industrial method for corrosion prevention.
What is the main component of 'Natural Gas' involved in combustion?
Correct Answer: C. Methane
Methane is the simplest hydrocarbon and the primary constituent of natural gas. Its combustion in oxygen produces carbon dioxide, water, and heat energy. It is considered a clean-burning fossil fuel compared to coal.
The digestion of food in our body is an example of which type of reaction?
Correct Answer: C. Decomposition reaction
Digestion involves breaking down complex food molecules into simpler substances like glucose. Biological catalysts called enzymes facilitate these decomposition reactions. This allows the body to absorb nutrients effectively.
Silver articles turn black after some time when exposed to air due to the formation of?
Correct Answer: B. Silver sulfide
Silver reacts with hydrogen sulfide present in the air to form a black coating. This process is a type of corrosion specifically known as tarnishing. It does not happen in perfectly clean and dry air.
Which of the following reactions is used in black and white photography?
Correct Answer: B. Decomposition of silver chloride
Silver chloride decomposes into silver and chlorine when exposed to sunlight. This photochemical reaction was the basis for traditional film photography. Silver bromide behaves in a very similar manner under light.
What is produced when Magnesium ribbon is burnt in air?
Correct Answer: B. Magnesium oxide
Magnesium reacts with atmospheric oxygen to form a white powder of magnesium oxide. The reaction produces a very bright white dazzling flame. It is a classic example of an oxidation and combination reaction.
A reaction in which heat is absorbed from the surroundings is called?
Correct Answer: A. Endothermic
Endothermic reactions require energy to proceed, resulting in a cooling effect on the surroundings. Melting of ice and evaporation of water are common physical endothermic processes. Many decomposition reactions are also endothermic.
The reaction between Barium Chloride and Sodium Sulfate to form Barium Sulfate is a?
Correct Answer: A. Double displacement
In this reaction, the two compounds exchange ions to form two new compounds. A white precipitate of Barium Sulfate is formed during this process. Double displacement reactions often result in the formation of a precipitate.
What does the symbol (aq) written after a chemical formula represent?
Correct Answer: C. Aqueous solution
The correct answer is 'Aqueous solution'. The symbol (aq) indicates that the substance is dissolved in water as a solvent. This helps in specifying the physical state of reactants and products in an equation. Water is the most common solvent used in chemical laboratories.
Which law states that mass is neither created nor destroyed in a chemical reaction?
Correct Answer: B. Law of Conservation of Mass
The Law of Conservation of Mass requires that the total mass of reactants equals the total mass of products. This is the fundamental reason why chemical equations must be balanced. It was famously established by Antoine Lavoisier.