Which method is used to obtain virus-free plants?

The freezing point of a $1.00 \, m$ aqueous solution of $HF$ is $-1.91^o C$. The freezing point depression constant of water $K_f$ is $1.86 \, K \, kg \, mol^{-1}$. The percentage of dissociation of $HF$ at this concentration is ......... $\%$

$y + x^2 = \frac{dy}{dx}$ has the solution

$A$ hollow sphere of radius $R$ is filled completely with an ideal liquid of density $\rho$. The sphere is moving horizontally with an acceleration $2g$,where $g$ is the acceleration due to gravity. If the minimum pressure of the liquid is $P_0$,then find the pressure at the centre of the sphere.

Two seconds after projection,a projectile is travelling in a direction inclined at $30^o$ to the horizontal. After one more second,it is travelling horizontally. What is the magnitude and direction of its velocity at the initial point?

When $25 \ g$ of a non-volatile solute is dissolved in $100 \ g$ of water,the vapour pressure is lowered by $0.225 \ mm$. If the vapour pressure of water at $20^{\circ}C$ is $17.5 \ mm$,what is the molecular weight of the solute?