Question

How many electrons flow when a current of 5 amperes passed through a solution for 193 seconds?
A. $6.022\times {{10}^{23}}$
B. $6.022\times {{10}^{22}}$
C. $6.022\times {{10}^{25}}$
D. $6.022\times {{10}^{21}}$

Answer 1

There is a relation between the current and the charge which is given by Q = I $\times$ t where Q is the charge present in the device, I is the amount of current that flows through the device and t is the time duration for which the current flows through the device. This formula is needed to solve this question.

Complete Solution :
-Electrochemistry is a branch of chemistry that deals with the conversion of chemical energy into electrical energy in electrochemical cells. Process is called electrolysis. When a metal is dipped in electrolyte, potential difference is created between the metal and electrolyte which allows flow of current.
-So, whenever current is passed through the solution, the ions in the solution dissociate themselves and move in different directions towards the electrodes. The circuit is completed and current flows as a result of difference in voltages.
-Reaction takes place at the electrodes. Electrode where oxidation occurs is called anode and electrode where reduction occurs is called cathode. These processes are governed by electrochemical series. The top elements behave as reducing agents and as we go down, the strength of the oxidizing agents increase.
-The electrons are transferred through the ions present in the solution. We know that the electrons are negatively charged particles with the charge of $1.6\times {{10}^{-19}}$ coulombs. A current in a circuit tells us nothing but the flow of electrons only but in the opposite direction.
-From the formula Q = It, we can find the charge present in the solution.
Q = 5A $\times$ 193 sec = 965 coulombs.
-Now we know that the charge present on 1 electron is $1.6\times {{10}^{-19}}$ coulombs. Knowing the value of total charge present and the charge on 1 electron, we can find the total number of electrons present in the solution.
-So, the total number of electrons will be $\begin{aligned} & \dfrac{965}{1.6\times {{10}^{-19}}} \\\ & \text{=6}\text{.022}\times \text{1}{{\text{0}}^{21}} \\\ \end{aligned}$
So, the correct answer is “Option D”.

Note: The current present in any circuit represents the electrons only. The electrons flow in a direction which is opposite to that of the flow of current. If the current in any circuit is zero, it indicates that the electrons are not able to flow in the circuit.
- Also always take care of the units while solving such questions. The current should be in amperes only and time in seconds.