Question

Write a balanced chemical equation for the reaction of solid strontium with iodine gas.

Short answer

The balanced chemical equation is Sr + I2 -> SrI2.

Step-by-step solution

Identify Reactants

The first step is to identify the reactants. In this reaction, we have solid strontium (Sr) and iodine gas (I2).

Write Unbalanced Equation

Write the chemical symbols for the reactants and the expected product. For this reaction, strontium will react with iodine to form strontium iodide, SrI2. The unbalanced chemical equation is Sr + I2 -> SrI2.

Balance the Strontium atoms

Look at the equation and compare the number of atoms of each element on both sides. Start with the metallic element, which is strontium in this case. Strontium atoms balance as there is one Sr atom on each side of the equation.

Balance the Iodine atoms

The iodine is diatomic (I2) but forms two iodide ions in SrI2. Therefore, to balance the iodine atoms, you need to have 2 iodine atoms on each side. This requires putting a coefficient of 2 in front of the iodide in the product: Sr + I2 -> SrI2 becomes Sr + I2 -> SrI2(2).

Update and Simplify the Equation

After placing the coefficient of 2 before SrI2 to balance iodine atoms, the correct formula would be SrI2, not SrI2(2). So now we update and simplify the equation: Sr + I2 -> SrI2. However, we need to balance the iodine correctly, placing the coefficient in front of the compound, not as part of the formula. So, the balanced equation now reads Sr + I2 -> SrI2.

Final Check

Make a final check to ensure the number of atoms of each element is equal on both sides of the equation. There is one strontium atom and two iodine atoms on both sides. The equation is balanced.

Key concepts

Chemical Equation Balancing

Understanding the concept of chemical equation balancing is like learning the art of maintaining symmetry in a seesaw. In chemistry, a reaction's 'seesaw' holds reactants on one side (the starting materials) and products on the other (the substances formed). The balancing act is to ensure that the number of atoms for each element is the same on both sides, preserving the fundamental Law of Conservation of Mass.

To start, write down the unbalanced equation which simply outlines the reactants and products. Next, compare the amount of each element on both sides and adjust using coefficients—whole numbers placed before chemical formulas to indicate how many units of that substance are involved. These coefficients multiply the number of atoms within the compound for each element they precede. For example, placing a 2 before H₂O means there are now 4 hydrogen atoms and 2 oxygen atoms involved.

The essential tool for this process is your chemical intuition, backed up by a set of guidelines: begin with the most complex compound or the one with the most elements, then balance elemental and diatomic molecules last. The gratification comes when every element 'weighs' the same on both sides, achieving balance without altering the original substances' chemical formulas—a common mistake among beginners.

Reactants and Products in Chemistry

In the realm of chemistry, reactions are akin to a culinary recipe, with reactants and products being the ingredients and the final dish, respectively. Reactants are the starting substances that undergo chemical changes, while products are the new substances formed as a result.

To visualize this concept, imagine baking a cake. Your reactants would be the flour, eggs, sugar, and butter you start with. Mix them in specific proportions, put them through a process—baking—and voilà, you get your cake, the product. Likewise, in our strontium and iodine example, solid strontium (Sr) and iodine gas (I₂) are the reactants. Under appropriate conditions, they react to form a new substance: strontium iodide (SrI₂), the product. The beauty of a chemical equation lies in its ability to succinctly represent this transformation from reactants to products, akin to how a recipe outlines the process of turning ingredients into a delightful dessert.

Stoichiometry

Diving deeper, the concept of stoichiometry is the chemical branch of bookkeeping; it deals with the quantitative relationships between the substances involved in a chemical reaction. Stoichiometry is the backbone calculation-wise, allowing chemists to predict how much product will be formed from a given quantity of reactants or how much reactant is required to produce a desired amount of product.

Role of Coefficients

Consider the coefficients in a balanced equation as 'molecular multipliers' that indicate the ratios at which reactants combine to form products. For instance, the balanced equation for the reaction of strontium with iodine tells us that one atom of strontium reacts with one molecule of iodine gas to produce one formula unit of strontium iodide.

Mole Concept

Incorporate the mole concept, as stoichiometry often operates in the realm of moles—a unit that measures the amount of substance. It enables you to calculate masses and volumes of reactants and products, given that the molar mass and gas volumes at standard conditions are known. Through stoichiometry, chemists can orchestrate the symphony of reactions, ensuring each note (element) is played in harmonious proportions to compose the final opus (product).