Among the following, the conformation that corresponds to the most stable conformation of meso-butane-2,3-diol is

For the given close packed structure of a salt made of cation X and anion Y shown below (ions of only one face are shown for clarity), the packing fraction is approximately (packing fraction = $${{packing\,efficiency} \over {100}}$$)

The calculated spin only magnetic moments of [ Cr(NH₃)₆]³⁺ and [CuF₆]3^$$-$$ in BM, respectively, are

(Atomic numbers of Cr and Cu are 24 and 29, respectively)

For the following reaction scheme, percentage yields are given along the arrow:



x g and y g are mass of R and U, respectively.

(Use : Molar mass (in g mol^$$-$$1) of H, C and O as 1, 12 and 16, respectively)

The value of x is ________.