The product $\begin{array}{*{20}{c}} {CH_2 - O - COCH_3} \\ {|} \\ {CH_2 - O - COCH_3} \end{array}$ is obtained by the reaction of which of the following?

$A$ certain metallic surface is illuminated with monochromatic light of wavelength $\lambda$. The stopping potential for the photoelectric current for this light is $3V_0$. If the same surface is illuminated with light of wavelength $2\lambda$,the stopping potential is $V_0$. The threshold wavelength for this surface for the photoelectric effect is:

Which one of the following is the mineral for tin?

If $4x^2 - 5xy + y^2 = 0$ represents a pair of lines with slopes $m_1$ and $m_2$,then the value of $|m_1 - m_2|$ equals

$3.2$ moles of hydrogen iodide were heated in a sealed bulb at $444 \, ^oC$ until the equilibrium state was reached. Its degree of dissociation at this temperature was found to be $22 \%$. The number of moles of hydrogen iodide present at equilibrium are:

Hydrolysis of $NCl_3$ gives $NH_3$ and $X$. Which of the following is $X$?