This form should be filled out using PEN only. Mistakes should be crossed throug

Question

This form should be filled out using PEN only. Mistakes should be crossed through with a single line only. What may account for any differences between the moles of electrons transferred in your reaction (z-experimental) compared to what should have theoretically been transferred (z-theoretical)? Why was using the moles of H_2 gas preferable to using the moles of O_2 gas when calculating z-experimental? Which of the following is/are true for the reaction performed in this experiment? (Cheek all that apply.) a. The number of electrons lost by one species is not necessarily equal to the number of electrons gained by the other. b. Electrons flow from the negative output to the positive output. c. Current flow refers to the direction of the flow of negative charges. d. Hydrogen was the reducing agent. e. Electrolyte ions carried charge from one cell to the other in the solution.

Explanation / Answer

(1) Here we can see there is a slight difference in the measured z-value and theoretical z-value. This may happen due to some experimental error. Let us discuss the reasons:

(a) There is some unavodiable reason that can cause the difference in the experimental values with actual. Like, there may have some sudden fuctuation of current during the experiment. This is we can't always control. This may raise some error.

(b) Also, we always try to keep the electrodes dry before experiment. But practically this is always not 100% possible. So, some moisture may remain in the electrode even after drying or washing. This may lead to some error in the experiment. This may cause the difference in actual and experimental values.

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(2) To calculate z-experimental, we always prefer to consider the moles of H2 over moles of O2. This is due tothe solubility profile of both of them in water. O2 is more soluble in water than H2. So, when we consider the volume of O2 during the experiment, it actually does not reflect the accurate volume. But in case of H2, it is almost insoluble in water. So, we can get much accurate volume of H2 during the experiment. This will lead to much accurate calculation of moles of H2. So, that is why, we prefer using the moles of H2 over moles of O2.

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(3) Let us consider each options one by one:

a. Here in the experiment, the electrons transfer is happening due to the current flow. Here the cell reactions are:

2H2O (l) ------> O2 (g) + 4H+(aq) + 4e- (Anode)

4H2O (l) + 4e--------> H2 (g) + 4OH- (aq) (Cathode)

So, we can see that practically electrons generated in anode are transferred to cathode to complete the reactions. There should not be any excess electrons remain, as the expelled electrons from anode drive the cathode reaction to get completed. So, the electron lost by one species has to be equal to the electron gained by another species. So, the first statement is False.

(b) Here the electron flow from the anode to cathode. But in electrolytic cell, anode is positive output and cathode is negative output. So, for electrolysis, the electron flow is from positive to negative output ( just opposite concept of electrochemical cell). So, the statement (b) is also False.

(c) For electrolytic cell, the current flows from positve output to negative output. Now, in this experiment, we can see the negative charged particle electrons also flow from positive to negative output. So, the current flow in electrolysis is in the direction of negative charge (electron) flow. So, the statement is True.

(d) Let us consider the reduction cell Cathode here (for electrolysis, cathode is the reduction cell):

4H2O (l) + 4e--------> H2 (g) + 4OH- (aq) (Cathode)

Here H2O is reduced by the electron flow to H2 gas. So, here hydrogen gas is justa product generated due to reduction. So, the reducing agent was the cathode electrode (metal used may be Al, Cu etc, not mentioned in the process given here). So, even Hydrogen gas is a good reducing agent, but here this is not used as reducing agent. So, the statement (d) is False.

(e) Electrolytes are those which carry charges from one cell to another. Now, the medium here can only be solution, as electrolytes are highly soluble in water. So, this statement is True for electrolysis.

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