QCM : Fundamentals of Chemistry and Matter — 10 questions

Explication

Chemistry is the branch of science that studies the preparation, properties, structure, and reactions of material substances. The other options refer to related but different aspects: the development of chemistry, ancient Indian atomic concepts, and substance classification, but do not define what chemistry itself is.

Explication

Acharya Kanda, around 600 BCE, proposed the concept of 'Paramanu' (atom), which is an early philosophical atomic theory predating Dalton's. Charaka and Sushruta were ancient Indian physicians known for Ayurveda, and Aryabhata was an astronomer and mathematician, not associated with atomic theory.

Explication

Classifying substances into elements, compounds, and mixtures helps in understanding their composition, properties, and how they can be separated or combined, which is essential for chemical analysis and synthesis.

Explication

The SI system was officially established by the 11th CGPM in 1960, providing a standardized framework for measurement units worldwide. The other dates are plausible but incorrect; 1920 and 1945 are before the formal establishment of SI, and 1980 is after the system was already in use.

Explication

The Law of Definite Proportions states that a chemical compound always contains the same elements in the same fixed ratio by mass. The Law of Multiple Proportions states that when two elements form more than one compound, the ratios of the masses of the second element that combine with a fixed mass of the first element are simple whole numbers. Therefore, they describe different aspects of chemical composition: one about fixed ratios in a single compound, the other about ratios in different compounds of the same elements.

Explication

Acharya Kanda, around 600 BCE, introduced the philosophical atomic theory by proposing the concept of 'Paramanu', which described atoms as indivisible and eternal particles forming all matter. Dalton and Democritus contributed to modern and Greek atomic theories respectively, but Acharya Kanda's early Indian concept predates them.

Explication

The mole concept was developed primarily to relate the number of microscopic particles like atoms and molecules to measurable quantities such as mass and volume, enabling quantitative analysis in chemistry.

Explication

To find the molecular formula from the empirical formula, you divide the molar mass of the compound by the empirical formula mass to find a factor, then multiply the empirical formula by this factor. This process scales the simplest ratio to the actual number of atoms in a molecule, which is a standard application of chemical formulas and equations.

Explication

The molar ratios of reactants and products, as given by the coefficients in a balanced chemical equation, are essential for stoichiometry calculations because they enable the calculation of quantities of reactants and products involved in a chemical reaction.

Explication

Solids are characterized by particles that are closely packed in an orderly arrangement with limited movement, which results in a definite shape and volume. This distinguishes them from liquids and gases, where particles are less tightly packed and have more freedom to move.