Matter, Atoms and Molecules RRB PYQ

To find the mass by mass percentage of the solution, use the formula: Mass percentage = (Mass of solute / Mass of solution) x 100. Mass of solute (salt) = 48 g; Mass of solvent (water) = 320 g; Mass of solution = Mass of solute + Mass of solvent = 368 g. Mass percentage = (48/368) x 100 ≈ 13.04%.

Neon and argon are examples of monoatomic gases. A monoatomic gas is one in which atoms are not bound to each other.

A homogeneous mixture is defined by its uniform composition and appearance throughout, whereas a heterogeneous mixture has a non-uniform composition. Unlike heterogeneous mixtures, homogeneous mixtures cannot be separated by simple filtration; they usually require methods like evaporation or distillation. An example of a homogeneous mixture is salt dissolved in water, while sand in water is an example of a heterogeneous mixture.

The formula unit mass of CaO (Calcium Oxide) is 56u. This is calculated by adding the atomic masses of calcium (40.08u) and oxygen (15.999u). Calcium Oxide (CaO), also known as quicklime, is a white, caustic, alkaline crystalline solid at room temperature.

The correct match is: A-IV, B-II, C-I, D-III. A-IV: 'Atomic mass of an element is not its actual mass but relative mass.' B-II: 'With the help of STM, it is possible to take the photograph of some atoms.' C-I: 'Atoms of different elements may have same masses.' D-III: 'Atoms have been found to be made up of sub-atomic particles.'

A proton is positively charged and its mass is taken as one unit. In atomic physics, a proton's mass is approximately 1.67x10^-27 kg, which is taken as one atomic mass unit (amu). An electron is a stable, negatively charged fundamental subatomic particle that orbits the nucleus, possessing a mass of roughly 9.11x10^-31 kg. A neutron is a fundamental subatomic particle found in the nucleus of every atom (except hydrogen), possessing no net electric charge and a mass slightly greater than a proton.

In Sulphur (S), the molecular form is S8, meaning each Sulphur molecule contains 8 atoms. This gives Sulphur the maximum number of atoms in its molecular form compared to Phosphorus (P4), which has 4 atoms, and Argon (Ar) and Neon (Ne), which are noble gases and exist as monoatomic (single atom) elements under standard conditions. Therefore, Sulphur has the most atoms in its molecular form.

The reaction AgNO3 + NaCl → AgCl + NaNO3 is not a redox reaction. It is a double displacement (metathesis) reaction, where ions are exchanged between two compounds without any change in oxidation states. In contrast, the other reactions involve changes in oxidation states, making them redox reactions.

The atomic mass of sodium and the atomic mass of chlorine need to be added to calculate the formula unit mass of sodium chloride. The atomic mass of sodium is approximately 23u and that of chlorine is 35.5u. Formula unit mass of NaCl = 23u + 35.5u = 58.5u.

The electronic configuration of carbon (C) is 1s2 2s2 2p2, meaning carbon has 6 electrons distributed in two shells: the K shell (which holds 2 electrons) and the L shell (which holds 4 electrons). Therefore, carbon uses two shells to accommodate its 6 electrons, so the correct answer is two.