Problem 63 - Chemistry Matter and Change

Question

Identify the reactants in the following reaction: When potassium is dropped into aqueous zinc nitrate, zinc and aqueous potassium nitrate form.

Step-by-Step Solution

Answer

The reactants in the given reaction are Potassium (K) and Aqueous Zinc Nitrate (Zn(NO3)2).

Step 1: Write down the chemical reaction

Write down the given reaction in words: Potassium + Aqueous Zinc Nitrate -> Zinc + Aqueous Potassium Nitrate

Step 2: Convert the reaction to a balanced chemical equation

Convert the word equation to a balanced chemical equation: 2 K (s) + Zn(NO3)2 (aq) -> Zn (s) + 2 KNO3 (aq)

Step 3: Identify the reactants

Reactants are the substances on the left side of the arrow in a balanced chemical equation. In this case, the reactants are: Potassium (K) and Aqueous Zinc Nitrate (Zn(NO3)2).

Key Concepts

Reactants

In a chemical reaction, identifying the reactants is a fundamental step. Reactants are the substances that you start with before the reaction takes place. These substances undergo a transformation during the reaction to form new products. In the exercise, the reactants are Potassium (K) and Aqueous Zinc Nitrate (Zn(NO3)2).

Think of reactants as the chemical ingredients in a recipe. Just like how flour and sugar might be used to bake a cake, reactants are used to "bake" new chemical substances. In chemical equations, reactants are always located on the left side of the arrow (→). This arrow separates reactants from products, indicating that a reaction goes from reactants to products. Understanding what reactants are, and identifying them correctly, is key to mastering chemical equations.

Chemical Equation

A chemical equation is a symbolic representation of a chemical reaction. It shows which substances start and finish the reaction, namely the reactants and the products. Each substance in the equation is represented by its chemical formula. This formula gives the type and number of atoms in each molecule.

For example, in the exercise provided:

• The reactants are written as K (s) and Zn(NO3)2 (aq).
• The products are Zn (s) and KNO3 (aq).

The states of matter are also indicated, such as (s) for solid and (aq) for aqueous or dissolved in water.

Chemical equations are essential for visualizing the process of a reaction. They provide key information about the transformation of matter that occurs during the reaction. Writing and understanding chemical equations helps chemists to communicate precisely what happens in a chemical reaction.

Balancing Equations

Balancing equations is a crucial aspect of working with chemical reactions. Chemical equations must be balanced to follow the Law of Conservation of Mass, which states that mass cannot be created or destroyed in a chemical reaction. This means the number of atoms for each element must be the same on both sides of the equation.

To balance a chemical equation, you adjust the coefficients (the numbers before the molecules) until there are equal numbers of each type of atom on both sides. For the equation in the exercise:

• The equation is initially written from the word reaction: Potassium + Aqueous Zinc Nitrate -> Zinc + Aqueous Potassium Nitrate.
• We then adjust it to: 2 K (s) + Zn(NO3)2 (aq) -> Zn (s) + 2 KNO3 (aq), to ensure that zinc, nitrate, and potassium atoms are balanced.

Balancing ensures that the equation truly reflects the conservation of atoms and thus the physical realities of the reaction. It's like ensuring both sides of a seesaw are balanced so that it works perfectly. Practicing balancing equations strengthens your understanding of stoichiometry and the nature of chemical reactions.