Question

A gas can expand from 100ml to 250 ml under a constant pressure of 2atm.the work done by the gas is:
(A) 30.48 J
(B) 25 J
(C) 5 KJ
(D) 16 J

Answer 1

Hint : To answer this question, we first need to understand what pressure is. Pressure is defined as the product of force and area. For example, the pressure exerted by snow on a roof is equal to the weight of the snow divided by the roof's area. The most common source of pressure in chemistry is gases. You put gas inside a balloon when you blow it up.

Complete Step By Step Answer:
Work done – Work is defined as force multiplied by distance in physical sciences such as physics and chemistry. If there is movement in the force's direction, work is created. The joule is the SI unit of labor (J). This is the work done by a force of one newton (N) over a one-meter displacement (m).
Gas – One of the four basic states of matter is gas. Individual atoms, elemental molecules built from one type of atom, or compound molecules created from a variety of atoms make up a pure gas. A gas mixture, such as air, consists of a number of different pure gases.
\[W = - Pext.\Delta V \\
  Given: - Pext. = 2atm \\
  Vi = 100mL = 0.1L \\
  Vf = 250mL = 0.25L \\
  \Delta V = Vf - Vi = 0.25 - 0.1 = 0.15L \\
  \therefore W = - 2 \times 0.15 = - 0.3L - atm = - 30.4J \]
The presence of a negative symbol here denotes that the task is being done by the gas.
So, the total work done is 30.4 J
So, the final answer is option (A) i.e., 30.48 J.

Note :
As we saw in our discussion of particular heats, an expanding gas exerts a force on its surroundings, its expanding container, and so does work. The temperature can be kept constant if this energy is restored as quickly as it is withdrawn by a flow of heat into the gas.