D. The total number of valence electrons is 8 and D represents that. D also correctly uses the octet rule for N and duet rule for H.
<h2>The baking of a Pizza be Categorize as Endothermic Process</h2>
The baking of a pizza should be categorized as an endothermic process because the dough absorbs heat. An endothermic process is a method that absorbs energy from its surroundings which is habitually in the form of energy.
It can be a biochemical process like solving the salt in water or just the melting of ice. Therefore, the dough absorbs heat and it is categorized as an endothermic process.
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.
Atomic mass silicon = 28.085 u
1 mol Si ---------------- 28.085 g
? ------------------------ 245 g
245 x 1 / 28.085 =><span> 8.72 mol</span>
<span>answer A</span>