What is the molar solubility of $Ag_2CO_3$ $(K_{sp} = 4 \times 10^{-13})$ in $0.1 \ M \ Na_2CO_3$ solution?

$A$ long straight wire carrying a current of $30 ~A$ is placed in an external uniform magnetic field of induction $4 \times 10^{-4} ~T$. The magnetic field is acting parallel to the direction of current. The magnitude of the resultant magnetic induction in tesla at a point $2.0 ~cm$ away from the wire is
$\left(\mu_0=4 \pi \times 10^{-7} ~H/m\right)$

Which of the following is not used as a biopesticide?

$Fe$ is made passive by

The figure given below shows a small part of human lung where exchange of gases takes place. In which one of the options given below,the one part $A, B, C$ or $D$ is correctly identified along with its function?

Indicate the number of unpaired electrons in:
$(a)$ $P$ $(b)$ $Si$ $(c)$ $Cr$ $(d)$ $Fe$ and $(e)$ $Kr$