Matter, Atoms and Molecules RRB PYQ

A decomposition reaction is a type of chemical reaction where a single compound (reactant) breaks down into two or more simpler products. This reaction typically requires an external source such as heat, light, or electricity. An example is the decomposition of sodium chloride: 2NaCl → 2Na + Cl2.

Boyle's law or the pressure-volume law states that the volume of a given amount of gas held at constant temperature varies inversely with the applied pressure when the temperature and mass are constant.

A combustion reaction is characterized by an element or compound burning in the presence of oxygen, releasing heat and light. For example, carbon reacts with oxygen to form carbon dioxide while emitting energy: C + O2 → CO2 + heat and light. This reaction is commonly used in industries to harness energy from fuels.

The balanced chemical equation for the reaction is: 6CO2(g) + 12H2O(l) → C6H12O6(aq) + 6O2(g) + 6H2O(l). This represents the photosynthesis reaction with proper state symbols and balanced atoms on both sides.

Precipitation reactions are a type of double displacement reaction where dissolved substances react to form one or more solid products. In these reactions, ions are exchanged between ionic compounds in aqueous solutions, resulting in the formation of a precipitate. Double displacement reactions involve the swapping of positive and negative ions between two compounds, some of which are insoluble and precipitate out of the solution.

In option (a), both sides of the equation have the same number of atoms: magnesium (Mg) and 2 oxygen (O) atoms on the left side (LHS) are balanced with magnesium (Mg) and 2 oxygen (O) atoms in 2MgO on the right side (RHS). The equation 2Mg + O2 → 2MgO is balanced.

The chemical equation is: CuO + H2 → Cu + H2O. Here, hydrogen gains oxygen, increasing its oxidation state from 0 to +2, which is characteristic of an oxidation process.

Balancing chemical equations is essential to adhere to the law of conservation of mass, which states that mass cannot be created or destroyed in a chemical reaction. By balancing the equation, we ensure that the number of atoms for each element is the same on both sides, preserving the total mass and making accurate stoichiometric calculations possible.

The reaction that requires energy for breaking down the reactants is Decomposition. In a decomposition reaction, a single compound is broken down into two or more simpler substances. This process often requires energy input, which can come from heat, light, or electricity. A single reactant, calcium carbonate (CaCO3), absorbs heat energy and breaks down into two simpler substances: calcium oxide (CaO, also known as quicklime) and carbon dioxide gas (CO2). A decomposition reaction occurs when one complex compound splits into two or more products.

In redox reactions, statement I is correct because the loss of oxygen by a substance is a form of reduction, and statement II is also correct because the gain of hydrogen by a substance is another form of reduction. Both criteria—losing oxygen or gaining hydrogen—describe reduction in a chemical reaction.