What is the definition of a reflux? What happens to the solvent during a reflux experiment? What are three characteristics of a "good" solvent to use for refluxing? You are asked to reflux a solution for one hour. At what point does the reflux time start? What is the temperature of the solution during the reflux? Should you report a melting point as a single number or a range? How are the high and low endpoints of the range determined experimentally during the melting point experiment? What is the relationship between the purity of a compound and its melting point range? Briefly describe how a rotary evaporator works. What is likely to happen if cooling water is not run through the condenser when solvent is vaporized using a rotary evaporator? That is, where is the solvent likely to end up?

a. The returning of the process fluid after it has been cooled, condensed or heated in a distillation column or packing.

b. should be stable at high temperatures

   should not form other side products

   should be reactively inert

c. as a range

d. by taking a series of measurements

e. impure substances melt at lower temperatures.

Explanation:

a. In a reflux, the condensate is returned to the original flask or boiler.  This is keep heating the process fluid at a constant temperature without the use of additional fuel. In addition, it increased the molar fraction of the distillate (In other words, it promotes and increased purity in the product)

b.  A solvent should be stable, it should not undergo side reactions to form undesirable side products, the solvent should be stable at high temperatures. In addition, the solvent should be chemically inert if possible.

c. It is best to report as a range. Note the experiment is not an ideal set-up, the melting point is determined by many factors.

d. The melting points can be determined by taking a series of measurements graphically.

e. Impure substances lower the melting point.

explanation:

let the different atoms be x and y. each with four protons and same mass will be represented as follows.

mass number is number of protons + number of neutrons.

            and  

since, it is given that one has a negative charge while the other is neutral. therefore, there will be increase in number of protons and the atom will be represented as follows.

according to periodic table, mass number of beryllium is 9 and it has atomic number 4 so, the atoms will be and .  

the protons and neutrons will be located inside the nucleus whereas the electrons will be revolving around the nucleus.