Suggest two reasons why the mass deposited was different from the expected value

1) Dissolution of the copper anode

2) Time of the reaction

Explanation:

The figure shows the electrolysis of Copper Chloride using copper electrodes.

In aqueous solution, the ions present in the solution include:  H⁺, OH⁻. Cu²⁺ Cl⁻

The half equations for the reaction  are:

At rhe Anode (positive electrode) : 2Cl⁻(aq) - 2e = Cl₂(g)

At the Cathode (negative electrode) Cu²⁺ (aq) + 2e = Cu (s)

Hence copper ions are reduced at the cathode by gaining two electrons to form copper solid deposits. It is the mass of the deposited copper that the student measured over time.

Reasons why the actual mass is different  from the expected mass

1) Dissolution of the copper Anode: The electrodes used for this experiment are copper electrodes as both the positive and negative electrode.

Under the influence of an electric current, the copper anode will dissolve by gaining electrons and go into solution as copper II ions (Cu²⁺). thereby increasing the amount of copper ions in solution.

The aqueous copper ions from the anode and from the copper chloride (CuCl₂ (aq) electrolyte will migrate to the negative cathode, gain electrons, and get deposited as pure copper solid.  This increases the mass of copper solid deposited at the cathode.

2) Time: As the time of the reaction from zero to sixty (60) minutes under the influence of an electric current, more of the copper anode will dissolve, migrate to the cathode and get deposited as copper solid.

Hence as the time of the reaction increases, more of the copper ions will be deposited as copper solid thereby increasing the value of the actual mass of copper deposited.

assuming that your periodic table has eighteen columns, you should highlight   the four elements in the third column from the left of the table.

neutral atoms of elements after calcium contain d electrons. the energy of d orbitals of a particular main shell lies between the energy of the s and p orbitals of the next main shell. for example, electrons in the have energy higher than those in the orbital while lower than those of the orbital.

by the aufbau principle, electrons fill orbitals one at a time, starting from those of the lowest energy. the orbital is therefore filled right after orbitals and before orbitals.  

potassium has electron configuration and calcium . the s orbital of a main shell holds a maximum of two electrons. the next element would thus have the electron configuration and satisfy the requirements.

a neutral atom of the element contains three electrons on top of the most recent noble gas element. it should thus be placed in the third column of the periodic table. both scandium and yttrium would satisfy the conditions. an aufbau diagram indicates that the 4f orbital is filled before the 5d. however, it appears that exceptions exists for both lanthanum and actinium. neutral atoms of the two d-block elements also demonstrate the and should be highlighted as well.

a saline water is fed to a reverse osmosis unit at flow rate o rotameter connected to reject (retentate) line reads 8 installed in reject and permeate line reads 15.2 milli siemens/cm and 300 micro siemens/com respectively.