In which of the following is lead sulfate $(PbSO_4)$ soluble?

The dispersive powers of the materials of two lenses forming an achromatic combination are in the ratio of $4: 3$. If the effective focal length of the two lenses is $+60 ~cm$,then the focal lengths of the lenses should be:

$A$ and $B$ are ideal gases. The molecular weights of $A$ and $B$ are in the ratio of $1: 4$. The pressure of a gas mixture containing equal weights of $A$ and $B$ is $P \ atm$. What is the partial pressure (in $atm$) of $B$ in the mixture?

Silica is added to roasted copper ore during extraction in order to remove

Which of the following alcohols reacts most rapidly with alkali metals?

The metal ion present in vitamin $B_{12}$ is