The answer is B ( you could have just looked it up online)
Density can be calculated using the following rule:
Density = mass / volume
Therefore:
mass = density * volume
We are given that:
Density = 75 g/ml
volume = 12 ml
Substitute with these givens in the equation to get the mass as follows:
mass = density * volume
mass = 75 * 12
mass = 900 g
Rf value is the ratio of the distance traveled by the solute to that of the solvent front on the paper used in chromatographic separation.
From the image it is clear the distance traveled by solvent front = 7.3 cm
Distance traveled by the component -1 of the mixture = 1.4 cm
Distance traveled by the component -2 of the mixture = 3.0 cm
Distance traveled by the component -3 of the mixture = 4.5 cm
Distance traveled by the component -4 of the mixture = 6.5 cm
Rf value of component-1 = 
Rf value of component-2 = 
Rf value of component-3 = 
Rf value of component-4 = 
b) Samples can be separated from a mixture using chromatography as the relative affinities for the compounds towards the paper (stationary phase) and the solvent(mobile phase) are different. Each component spends different amounts of time on the stationary phase depending on it chemical nature. So, the components in a mixture can be separated based on their polarities and relative degrees of adsorption on the stationary phase.
Answer : The chemical formula for the compound is, 
Explanation :
When the element 'M' react with the
to give
.
The balanced chemical reaction is,

In this reaction, 'M' is in mono-atomic form and
is in diatomic form.
By the stoichiometry,
2 moles 'M' react with the 1 mole of
to give 2 moles of
.
Therefore, the chemical formula of the compound is, 
Explanation:
The given data is as follows.
= 286 kJ = 
= 286000 J
,

Hence, formula to calculate entropy change of the reaction is as follows.

= ![[(\frac{1}{2} \times S_{O_{2}}) - (1 \times S_{H_{2}})] - [1 \times S_{H_{2}O}]](https://tex.z-dn.net/?f=%5B%28%5Cfrac%7B1%7D%7B2%7D%20%5Ctimes%20S_%7BO_%7B2%7D%7D%29%20-%20%281%20%5Ctimes%20S_%7BH_%7B2%7D%7D%29%5D%20-%20%5B1%20%5Ctimes%20S_%7BH_%7B2%7DO%7D%5D)
= ![[(\frac{1}{2} \times 205) + (1 \times 131)] - [(1 \times 70)]](https://tex.z-dn.net/?f=%5B%28%5Cfrac%7B1%7D%7B2%7D%20%5Ctimes%20205%29%20%2B%20%281%20%5Ctimes%20131%29%5D%20-%20%5B%281%20%5Ctimes%2070%29%5D)
= 163.5 J/K
Therefore, formula to calculate electric work energy required is as follows.
= 
= 237.277 kJ
Thus, we can conclude that the electrical work required for given situation is 237.277 kJ.