The ratio of the ionization energy of a Bohr hydrogen atom to that of a Bohr hydrogen-like lithium atom is:

What is the concentration of nitrate ions if equal volumes of $0.1 \ M$ $AgNO_3$ and $0.1 \ M$ $NaCl$ are mixed together (in $M$)?

$A$ poster is to be printed on a rectangular sheet of paper of area $18 \ m^2$. The margins at the top and bottom of $75 \ cm$ each and at the sides $50 \ cm$ each are to be left. Then the dimensions i.e. height and breadth of the sheet so that the space available for printing is maximum,are . . . . . . respectively.

Which of the following statements is incorrect?

The angle between the lines whose direction cosines are $\left(\frac{\sqrt{3}}{4}, \frac{1}{4}, \frac{\sqrt{3}}{2}\right)$ and $\left(\frac{\sqrt{3}}{4}, \frac{1}{4}, \frac{-\sqrt{3}}{2}\right)$ is:

The synonym for water gas when used in the production of methanol is