Among $TiF_6^{2-}, CoF_6^{3-}, Cu_2Cl_2$ and $NiCl_4^{2-}$,the colourless species are:

Which process is used for the removal of hardness of water?

An iron load of $2 \ kg$ is suspended in air from the free end of a sonometer wire of length $1 \ m$. $A$ tuning fork of frequency $256 \ Hz$ is in resonance with $\frac{1}{\sqrt{7}}$ times the length of the sonometer wire. If the load is immersed in water,the length of the wire in metres that will be in resonance with the same tuning fork is (Specific gravity of iron $= 8$)

In a balanced meter bridge,the resistance of the bridge wire is $0.1 \Omega/cm$. An unknown resistance $X$ is connected in the left gap and $6 \Omega$ in the right gap. The null point divides the wire in the ratio $2:3$. Find the current drawn from a battery of $5 \text{ V}$ having negligible internal resistance. (in $A$)

Which of the following metals releases hydrogen gas upon reaction with cold and dilute $HNO_3$?

$A$ particle of mass $m$ and charge $q$ is in an electric and magnetic field,given by $\vec{E} = 2 \hat{i} + 3 \hat{j}$ and $\vec{B} = 4 \hat{j} + 6 \hat{k}$. The charged particle is shifted from the origin to the point $P(1, 1)$ along a straight path. The magnitude of the total work done on it is: (in $q$)