Question

An insulated rigid vessel contains a mixture of fuel and air. The mixture is ignited by a minute spark. The contents of the vessel experience

• A. Increase in temperature, pressure and energy
• B. Decrease in temperature, pressure and energy
• C. Increase in temperature and pressure but no change in energy
• D. Increase in temperature and pressure but decrease in energy

Answer 1

The correct option is C Increase in temperature and pressure but no change in energy

(c)
When the mixture is ignited by a minute spark, it will result in combustion of fuel, due to which:
1. Increaase in temperature
2. As it is rigid vessel, so volume will be constant, then pressure will increase.
3. Also, as it is an insulated vessel, so $\delta Q=0$ hence energy generated due to the combustion will be stored as internal energy of combustion products, it means no change in energy.
Note: Negligible change in energy due to spark as it is given in minutes.