The question asks to identify the scientist who proposed the Law of Conservation of Mass and the year it was proposed. This requires knowledge of fundamental chemistry history.
Correct Option: A) Antoine Lavoisier (French chemist), 1789
Antoine Lavoisier, a French nobleman and chemist, is widely regarded as the "Father of Modern Chemistry." He meticulously conducted experiments, especially on combustion, and demonstrated that mass is conserved in chemical reactions. He published his findings, including the Law of Conservation of Mass, in his seminal work Traité Élémentaire de Chimie (Elementary Treatise of Chemistry) in 1789. This year marks a pivotal moment in the history of chemistry, as it shifted the field from qualitative to quantitative analysis.
The question asks for the correct statement of the Law of Conservation of Mass. We need to evaluate each option based on the fundamental principles of chemistry and physics.
Correct Option: C) Matter can neither be created nor destroyed in a chemical reaction — the total mass of all reactants equals the total mass of all products
The Law of Conservation of Mass states that mass in an isolated system is neither created nor destroyed by chemical reactions or physical transformations. Lavoisier's experiments were crucial in establishing this law. To demonstrate this, one must ensure that no matter escapes or enters the system during the reaction.
Correct Option: D) He performed reactions in a closed container (sealed flask) and weighed reactants and products carefully before and after the reaction. This method directly addresses the principle of conservation of mass by ensuring that all matter involved in the reaction is accounted for, preventing any loss or gain of mass from the system.
Which of the following statements correctly illustrates the Law of Conservation of Mass?
2Mg + O₂ → 2MgO; 48 g of magnesium burns to give 48 g of magnesium oxide
2H₂O → 2H₂ + O₂; 36 g of water gives 4 g of hydrogen and 16 g of oxygen
C + O₂ → CO₂; 12 g of carbon burns in 32 g of oxygen to give 32 g of carbon dioxide
CaCO₃ → CaO + CO₂; 100 g of calcium carbonate gives 56 g of calcium oxide and 44 g of carbon dioxide
The Law of Conservation of Mass states that mass can neither be created nor destroyed in a chemical reaction. This means the total mass of the reactants must be equal to the total mass of the products. We need to check each option to see which one adheres to this law.
Correct Option: D) CaCO₃ → CaO + CO₂; 100 g of calcium carbonate gives 56 g of calcium oxide and 44 g of carbon dioxide
The question asks to identify the scientist who formulated the Law of Definite Proportions (also known as the Law of Constant Composition) and the year of its formulation. This requires knowledge of fundamental chemical laws and their historical context.
A) Joseph Proust (French chemist), 1799
Joseph Proust, a French chemist, is famously credited with formulating the Law of Definite Proportions (or Law of Constant Composition) in 1799. His experiments demonstrated that chemical compounds always contain the same proportion of elements by mass, regardless of their origin or method of preparation. For example, he showed that samples of copper carbonate, whether natural or synthetic, always had the same proportions of copper, carbon, and oxygen.
The question asks for the correct statement of the Law of Definite Proportions, also known as the Law of Constant Composition. This is a fundamental law in chemistry that describes the composition of chemical compounds.
D) A given compound always contains exactly the same elements combined together in the same fixed proportion by mass, regardless of its source or method of preparation.
This statement perfectly aligns with the definition of the Law of Definite Proportions. It emphasizes that the elemental composition by mass is constant for any specific compound, irrespective of how it was formed or where it was obtained from.