Demystifying Standard Reduction Potentials: The Language of EMF in Chemistry

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Welcome to our captivating journey into the world of chemistry and electromotive force (EMF). In our latest video, "Demystifying Standard Reduction Potentials: The Language of EMF in Chemistry," we'll decode the intricate concept of standard reduction potentials, unveiling their significance in the realm of galvanic cells.

EMF, or electromotive force, is a pivotal measure in electrochemistry, quantifying the potential difference across the electrodes of a galvanic cell when drawing a negligibly small current. Put simply, it's the voltage of a galvanic cell, representing the difference in reduction potentials between the two electrodes that make up the cell.

Reduction potential is a key player in this narrative. It reflects an element's propensity to undergo reduction, with lower reduction potentials indicating a higher tendency to be oxidized. Now, if you're wondering how we measure these potentials, you're in for a treat.

Enter the "Standard Reduction Potential." This intriguing concept reveals that measuring the reduction potential of a half-cell requires not one, but two different half-cells working together to generate a measurable EMF. But we can't do this without a standard reference. The standard hydrogen electrode, featuring hydrogen gas at 1 atmosphere pressure, bubbles around a platinum electrode in a solution of 1M hydrogen ions. This becomes our baseline, with E Hydrogen set at 0.00V for comparison.

Moving up and down the list of reduction potentials, we'll uncover the reactivity of various elements. Those at the top tend to be oxidized, while those at the bottom are formidable oxidizing agents and tend to reduce. These values represent their reduction potentials, crucial in determining EMF. The video will navigate the table of standard reduction potentials, culminating in understanding cell potentials, which are the sum of oxidation potential and reduction potential.

We'll also delve into the significance of the EMF sign. A positive cell potential denotes spontaneous reactions, typical in Galvanic cells, while a negative cell potential signifies that energy input is required for the reaction, commonly seen in electrolytic cells.

Join us in this electrifying adventure through the world of EMF and standard reduction potentials, and gain a deeper appreciation of their role in the fascinating world of chemistry. Hit play and start your journey today!

EMF

They are a measure of electromotive force (emf). The EMF of a galvanic cell is the potential difference across the electrodes when a negligibly small current is being drawn.

In simpler terms, the EMF or voltage of a galvanic cell is the difference in the reduction potentials between the two electrodes making up the cell.

Reduction Potential

• The ability or tendency of an element to undergo reduction.
• The lower the reduction potential, the more tendency to be oxidised.

Standard Reduction Potential

The reduction potential of a half-cell cannot be directly measured alone. 2 different half-cells are required to generate measurable emf. Reduction potentials are measured against a standard hydrogen electrode as a reference.

For individual cells to be compared, a standard needs to be made.
• The hydrogen half-cell consists of hydrogen gas at a pressure of 1 atmosphere, bubbling around an inert platinum electrode in a solution of 1M hydrogen ions is used as this standard.

E Hydrogen = 0.00V as a set standard for comparison between other half-cells. The standard reduction potential of an electrode is the potential of that electrode in its standard state relative to the standard hydrogen electrode with standard conditions.

• Moving up the list, the reactivity of the metals increases. Hence, elements at the top tend to be oxidised (reduce species lower in the table.)
• The reactants at the bottom of the list are non-metals and transitional metals. They are the strongest oxidising agents, and so they tend to reduce.
• The product at the top of the list is reactive metals and hydrogen. They are the strongest reducing agents, and so they tend to oxidise
• These values represent their reduction potentials.
• The emf is obtained from the table of standard reduction potentials.
• Cell potentials are the sum of oxidation potential and reduction potential.
Sign of the EMF
• A positive cell potential indicates that the reaction occurs spontaneously, as in Galvanic cells.
• A negative cell potential indicates that energy input is required for the reaction, as in electrolytic cells.