At \(900^{\circ} \mathrm{C}\) titanium tetrachloride vapor reacts with molten magnesium metal to form solid titanium metal and molten magnesium chloride. (a) Write a balanced equation for this reaction. (b) What is being oxidized, and what is being reduced? (c) Which substance is the reductant, and which is the oxidant?

Balancing chemical equations is a crucial skill in chemistry that ensures the law of conservation of mass is respected, meaning that the number of atoms of each element is the same on both sides of the equation. Let's delve into the process of balancing the equation TiCl4 + Mg → Ti + 2 MgCl2.

When balancing, start by listing the number of atoms of each element in the reactants and products. In our problem, we have titanium, chlorine, and magnesium to consider. The initial equation shows that chlorine is out of balance, with 4 atoms on the reactant side and only 2 on the product side. By doubling the amount of MgCl2, you balance the chlorine atoms. The titanium and magnesium atoms are already balanced—one atom each on both sides.

Thus, the corrected equation becomes TiCl4 + 2 Mg → Ti + 2 MgCl2, with equal numbers of each type of atom on either side, reflecting the mass conservation principle.

Understanding oxidation states is key to grasping redox reactions. The oxidation state, often referred to as oxidation number, is a measure of the degree of oxidation of an atom in a substance. It helps us track the transfer of electrons during the reaction.

In our reaction, TiCl4 has a titanium (Ti) atom with an oxidation state of +4 and chlorine (Cl) with -1 each, summing to zero. Magnesium (Mg) in its elemental form has an oxidation state of 0, while in MgCl2, magnesium exhibits a +2 oxidation state because it has lost two electrons, and each chlorine has an oxidation state of -1. By comparing these states, we can see that Ti is reduced as it goes from +4 to 0, and Mg is oxidized as it goes from 0 to +2, indicating that the transfer of electrons is indeed occurring.

In redox chemistry, identifying the reductant and oxidant is fundamental. The reductant (also known as the reducing agent) is the substance that donates electrons, thus being oxidized itself. Conversely, the oxidant (oxidizing agent) accepts electrons, undergoing reduction.

In the given equation, magnesium's oxidation state increases from 0 to +2, indicating it loses electrons and, hence, is the reductant. Titanium tetrachloride, on the other side, gains electrons as Ti's oxidation state decreases from +4 in TiCl4 to 0 in Ti, making TiCl4 the oxidant. Understanding the role of each substance in a redox reaction is essential, as it lays the groundwork for predicting reaction outcomes and crafting further chemical equations.