The number of atoms in $100 \text{ g}$ of an $fcc$ crystal with density $d = 10 \text{ g/cm}^3$ and cell edge equal to $100 \text{ pm}$ is equal to:

The ratio of the mass percentages of $C$ and $H$,and $C$ and $O$ of a saturated acyclic organic compound $X$ are $4:1$ and $3:4$ respectively. Then,the moles of oxygen gas required for the complete combustion of two moles of organic compound $X$ is:

In a bicycle,the radius of the rear wheel is twice the radius of the front wheel. If $r_F$ and $r_r$ are the radii,and $v_F$ and $v_r$ are the speeds of the topmost points of the wheels respectively,then:

The $EAN$ of platinum in potassium hexachloroplatinate $(IV)$ is :

If the number of $5$-element subsets of the set $A = \{a_1, a_2, \ldots, a_{20}\}$ of $20$ distinct elements is $k$ times the number of $5$-element subsets containing $a_4$,then $k$ is

$F_{pp}$,$F_{nn}$,and $F_{np}$ are the nuclear forces between proton-proton,neutron-neutron,and neutron-proton respectively. Then the relation between them is: