The first shell can hold up to 2 electrons, the second shell can hold up to 8 (2 + 6) electrons, the third shell can hold up to 18 (2 + 6 + 10) and so on.
Answer:
a. The phenolphthalein acts as a color changing indicator to signal the endpoint of the reaction.
Explanation:
Phenolphthalein is an organic substance with chemical formula 
.
It is a substance commonly used in acid-base titrations to indicate the end point in the titration because phenolphthalein is colorless in acidic solutions but turns a purplish-pink color in basic solutions.
In this way it helps visually to notice when the final point of the titration has been reached.
The noble gases are relatively unreactive because they have a stable octet of valence electrons.
Thus, they do not tend to undergo reactions in which they will gain or lose valence electrons,
However, <em>only He, Ne, and Ar are inert</em>. Kr and Xe combine with other highly reactive elements to form stable compounds.
The gas molecules move between the system and the surroundings follow PV=nRT.
<h3>What are molecules?</h3>
The smallest particle of a substance has all of the physical and chemical properties of that substance.
An increase in pressure pushes the molecules closer together, reducing the volume. If the pressure is decreased, the gases are free to move about in a larger volume.
In the kinetic theory of gasses, increasing the temperature of a gas increases in average kinetic energy of the molecules, causing increased motion.
The reduction in the volume of the gas means that the molecules are striking the walls more often increasing the pressure, and conversely if the volume increases the distance the molecules must travel to strike the walls increases and they hit the walls less often thus decreasing the pressure.
At constant temperature and pressure the volume of a gas is directly proportional to the number of moles of gas. At constant temperature and volume the pressure of a gas is directly proportional to the number of moles of gas.
Learn more about molecules here:
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