Which of the following substances undergoes sublimation?

Which of the following salts is used in the bead test for the qualitative analysis of inorganic substances?

The coefficient of static friction,$\mu_s$ between block $A$ of mass $2\,kg$ and the table as shown in the figure is $0.2$. What would be the maximum mass value of block $B$ so that the two blocks do not move (in $,kg$)? The string and the pulley are assumed to be smooth and massless. $(g = 10\,m/s^2)$

In the diagram,$I_1$ and $I_2$ are the strengths of the currents in the loop and the infinitely long straight conductor,respectively. Given $OA = AB = R$. The net magnetic field at the centre $O$ is zero. Then the ratio of the currents in the loop and the straight conductor $(I_1/I_2)$ is:

The correct order of hydration enthalpies of alkali metal ions is

The variance of $20$ observations is $5$. If each observation is multiplied by $2$,then the variance of the resulting observations is: