Which of the following pairs of substances cannot exist together in a solution?

The potential difference between $A$ and $B$ in the figure is .............. $V$.

The instantaneous angular position of a point on a rotating wheel is given by the equation $\theta(t) = 2t^3 - 6t^2$. The torque on the wheel becomes zero at $t = $ ....... $\text{sec}$.

The first diffraction minimum due to a single slit diffraction is seen at $\theta = 30^o$ for light of wavelength $5000 \, \mathring{A}$ falling perpendicularly on the slit. The width of the slit is

The transformed equation of $3x^2 + 3y^2 + 2xy = 2$,when the coordinate axes are rotated through an angle of $45^{\circ}$,is

At $27^{\circ} C$,$500 \ mL$ of helium diffuses in $30 \ minutes$. What is the time (in hours) taken for $1000 \ mL$ of $SO_2$ to diffuse under the same experimental conditions?