Question

The African bombardier beetle stenaptinus insignis can emit a jet of defensive spray from the movable tip of its abdomen. The beetle's body has reservoirs of two different chemicals. When the beetle is disturbed, these chemicals are combined in a reaction chamber producing a compounds that is warmed from ${20}^o$C to ${100}^o$C by the heat of reaction. The high pressure produced allows the compound to the sprayed out at speeds 19 ms${}^{-1}$ scaring away predators of all kinds. Assume specific heat of two chemicals and the spray to be same as that of water $[4.19\times {10}^{3}J(kgK{)}^{-1}]$ and initial temperature of chemicals to be ${20}^o$C. How many times does the pressure increase?

• A. 1.5
• B. 2.3
• C. 1.9
• D. 1.28

Answer 1

The correct option is D 1.28

$\frac{P_1}{T_1}=\frac{P_2}{T_2}$
or $\frac{P_2}{P_1}=\frac{T_2}{T_1}=\frac{373}{293}=1.28$