Select the mismatched pair from the following.

Oxalic acid reacts with concentrated $H_2SO_4$ to give a mixture of two gases. When this mixture is passed through caustic potash,one of the gases is absorbed. What is the product formed by the absorbed gas with caustic potash?

Passage cells are thin-walled cells found in

$A$ wire fixed at the upper end stretches by length $l$ by applying a force $F$. The work done in stretching is

The force $\vec{F} = 7\widehat{i} + 3\widehat{j} - 5\widehat{k}$ acts on a particle whose position vector is $\vec{r} = \widehat{i} - \widehat{j} + \widehat{k}$. What is the torque of the given force about the origin?

Which of the following is not a chromophore?