Consider two electrochemical reactions: A and B. Reaction A results in the transfer of 2 mol of electrons per mole of reactant and generates a current of 5 Amps on an electrode 2 cm2 in area. Reaction B results in the transfer of 3 mol of electrons per mole of reactant and generates a current of 15 Amps on an electrode having 5 cm2 in area. What are the net reaction rates for reactions A and B (in mol reactant per square centimeter per second)

See explaination

Explanation:

The rate of the electrochemical reaction per unit area is given by

r=\frac{i}{nFA}

where r is the Reaction Rate (in mol s-1 cm-2)

i is the Current Generated (in A)

n is the Number of moles of electrons per mole of reactant

F is Faraday's Constant= 96,500 C mol-1

A is the Electrode Area (in cm2)

(Unit of current should be expressed in terms of Columb per second, C s-1 to obtain reaction rate in mol s-1 cm-2)

Net Reaction Rate for Reaction A:

Given: Number of moles of A, n=2 moles

Current generated, i=5 A=5 C s-1

Electrode Area, A= 2cm2

Thus reaction rate is

\mathbf{r=\frac{5 C s^{-1}}{2*96500 C mol^{-1} *2 cm^{2}}= 1.3*10^{-5} mol s^{-1} cm^{-2}}

Net Reaction Rate for Reaction B:

Given: Number of moles of B, n=3 moles

Current generated, i=15 A=15 C s-1

Electrode Area, A= 5cm2

Thus reaction rate is

\mathbf{r=\frac{15 C s^{-1}}{3*96500 C mol^{-1}*5cm^{2}}= 1.036*10^{-5} mol s^{-1} cm^{-2}}

Reaction A has higher net reaction rate.

the answer is learned

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.