Which of the following will have the minimum osmotic pressure?

$A$ solid has a structure in which $W$ atoms are located at the corners of a cubic lattice,$O$ atoms at the centre of edges,and $Na$ atoms at the centre of the cube. The formula for the compound is

Which one of the following statements is not correct?

Oxalic acid reacts with concentrated $H_2SO_4$ to give a mixture of two gases. When this mixture is passed through caustic potash,one of the gases is absorbed. What is the product formed by the absorbed gas with caustic potash?

Which of the following hydrides is electron-deficient?

$A$ container of mass $m$ is pulled by a constant force $F$. Inside the container,a second block of the same mass $m$ is placed,connected to the wall by a massless spring of constant $k$. Initially,the spring is at its natural length. Find the velocity of the container at the instant when the compression in the spring is maximum for the first time.