Oedema, or swelling, occurs when fluid accumulates in the body's tissues. This can happen due to various reasons, including prolonged sitting, which can reduce blood and lymph flow, leading to fluid buildup.
Soaking the feet in warm salt water can help reduce this swelling. The warmth of the water increases blood flow, while the salt (sodium chloride) in the water helps draw fluid out of the tissues.
The correct answer is (B) Osmosis. Soaking the feet in warm salt water reduces swelling by increasing the solute concentration outside the cells, which draws water out of the cells through osmosis.
Osmosis is the process by which solvent molecules move from a region of lower solute concentration to a region of higher solute concentration through a semi-permeable membrane. In this case, the swollen feet have a higher concentration of fluid inside the cells (due to fluid accumulation) compared to the surrounding environment (warm salt water). Soaking the feet in warm salt water helps the fluid move out of the cells (osmosis), thereby reducing the swelling.
Other options:
(A) Reverse osmosis is a process where solvent moves from a higher concentration to a lower concentration, typically used in water purification. It is not related to this case.
(C) Edema refers to the condition of fluid retention and swelling, but it does not explain the mechanism behind the reduction of swelling.
(D) Diffusion is the movement of molecules from a region of higher concentration to a region of lower concentration, but it does not involve a semi-permeable membrane as in osmosis.
According to the generally accepted definition of the ideal solution there are equal interaction forces acting between molecules belonging to the same or different species. (This is equivalent to the statement that the activity of the components equals the concentration.) Strictly speaking, this concept is valid in ecological systems (isotopic mixtures of an element, hydrocarbons mixtures, etc.). It is still usual to talk about ideal solutions as limiting cases in reality since very dilute solutions behave ideally with respect to the solvent. This law is further supported by the fact that Raoult’s law empirically found for describing the behaviour of the solvent in dilute solutions can be deduced thermodynamically via the assumption of ideal behaviour of the solvent.
Answer the following questions:
(a) Give one example of miscible liquid pair which shows negative deviation from Raoult’s law. What is the reason for such deviation?
(b) (i) State Raoult’s law for a solution containing volatile components.
OR
(ii) Raoult’s law is a special case of Henry’s law. Comment.
(c) Write two characteristics of an ideal solution.
A wooden block of mass M lies on a rough floor. Another wooden block of the same mass is hanging from the point O through strings as shown in the figure. To achieve equilibrium, the coefficient of static friction between the block on the floor and the floor itself is