Question

From the following list, identify those elements that are easier to oxidize than \(\mathrm{H}_{2}(\mathrm{g})\) (a) \(\mathrm{Cu}\) (b) \(\mathrm{Zn}\) (c) \(\mathrm{Fe}\) (d) \(\mathrm{Ag}\) (e) \(\mathrm{Cr}\)

Short answer

Zn, Fe, and Cr are easier to oxidize than H₂.

Step-by-step solution

Understanding Oxidation and the Standard Hydrogen Electrode (SHE)

Oxidation refers to the loss of electrons. For a metal to be easier to oxidize than hydrogen gas, it must have a higher tendency to lose electrons. The Standard Electrode Potentials (E°) table is used to compare this. The Standard Hydrogen Electrode (SHE) is used as a reference with an E° value of 0.00 V.

Examine the Standard Electrode Potentials

Locate the standard electrode potentials for each given element in the electrochemical series: - Cu: E° = +0.34 V Zn: E° = -0.76 V Fe: E° = -0.44 V Ag: E° = +0.80 V Cr: E° = -0.74 V Materials with negative voltages in the series indicate a greater tendency to lose electrons (oxidize) than hydrogen.

Compare Potentials with SHE

Compare each metal's standard electrode potential with hydrogen's, which is 0.00 V. - Cu (+0.34 V) and Ag (+0.80 V) have positive potentials, indicating they are not easier to oxidize than H₂. - Zn (-0.76 V), Fe (-0.44 V), Cr (-0.74 V) have negative potentials, meaning they are easier to oxidize than H₂.

List the Easier-to-Oxidize Elements

Based on their standard electrode potentials, identify Zn, Fe, and Cr as the elements with negative E° values, indicating they are easier to oxidize than hydrogen gas.

Key concepts

Oxidation

In chemistry, oxidation is a fundamental concept that describes the process of losing electrons. Imagine you have a group of atoms, and one of them gives away some of its electrons. That atom is being oxidized. This is an essential concept because nearly all chemical reactions involve the transfer of electrons in some form.
In a redox reaction, which stands for reduction-oxidation reaction, one substance gets oxidized while another gets reduced (gains electrons). You can think of it like a dance where one partner moves away (loses electrons) while another partner moves in closer (gains electrons).
Furthermore, elements have different tendencies to lose electrons. This tendency is crucial when studying electrochemical cells or batteries. Elements like zinc, iron, or chromium willingly give up electrons more readily than hydrogen, making them prone to oxidation. Recognizing which materials oxidize easily helps in designing batteries or even preventing rust.

Standard Electrode Potential

Standard Electrode Potential (E°) is a measure of the tendency of a chemical species to be reduced, measured in volts under standard conditions (which include a concentration of 1 M, a pressure of 1 atm, and a temperature of 25°C). This value tells us how likely it is for a chemical substance, like a metal, to gain electrons. When talking about oxidation, we refer to the opposite process, the tendency to lose electrons. Metals with a negative E° value are more prone to oxidation under standard conditions. That's why they are more willing to donate electrons than hydrogen, which is set at 0.00 V in comparisons. To find out if a metal is easier to oxidize than hydrogen, you compare its standard electrode potential with hydrogen's. If its E° is negative, like in zinc and iron, it's more easily oxidized than hydrogen. This contrasting value is the secret behind understanding redox reactions and the efficiency of electrochemical cells like batteries.

Electrochemical Series

The Electrochemical Series, also known as the Activity Series, is a list of elements organized by their standard electrode potentials. This sequence provides a quick way to determine which elements will oxidize or reduce more readily compared to others. In this series, metals with a lower (more negative) standard electrode potential are placed higher up and are more inclined to oxidize or lose electrons. Elements like zinc and chromium, found higher in this series, are excellent candidates for providing electrons in redox reactions.
Within the electrochemical series, hydrogen has a standard midpoint value of 0.00 V. Metals with E° values below this, such as iron and chromium, are favorable to oxidize, meaning they readily undergo oxidation and consequently act as good reducing agents. Understanding the electrochemical series is vital for those working with reactions involving metals, such as electroplating, corrosion prevention, and creating effective batteries. It offers a comprehensive guide for predicting the outcome and feasibility of chemical reactions.