Problem 4 - General Chemistry: Principles and Modern Applications

Question

A 1.446 g sample of potassium reacts with 8.178 g of chlorine to produce potassium chloride as the only product. After the reaction, 6.867 g of chlorine remains unreacted. What mass of potassium chloride was formed?

Step-by-Step Solution

Answer

The mass of potassium chloride formed is 2.757 g.

Step 1: Calculate the total weight of potassium and chlorine before the reaction

Add the weight of potassium and chlorine to find the total weight before the reaction:\(1.446 g (potassium) + 8.178 g (chlorine) = 9.624 g\)

Step 2: Find the weight of chlorine that reacted

Subtract the weight of chlorine that remained unreacted from the total weight of chlorine before the reaction to find the weight of chlorine that reacted: \(8.178 g (chlorine initially) - 6.867 g (chlorine unreacted) = 1.311 g (chlorine that reacted)\)

Step 3: Calculate the weight of produced potassium chloride

Add the weight of the reacted potassium and chlorine to find the weight of potassium chloride that was formed: \(1.446 g (potassium) + 1.311 g (chlorine) = 2.757 g\)

Key Concepts

Chemical Reactions

Chemical reactions involve transforming the starting substances, known as reactants, into new substances called products. In the exercise, potassium ( K ) reacts with chlorine ( Cl_2 ) to produce potassium chloride ( KCl ). During a chemical reaction:

• Atoms are rearranged to form new products.
• No new atoms are created or destroyed.
• The properties of the products can be vastly different from those of the reactants.

In our context, potassium and chlorine combine in a specific way to generate potassium chloride, which has unique properties compared to its individual components.

Mass Conservation

The principle of mass conservation states that the mass of the reactants in a chemical reaction will equal the mass of the products. This means the total mass remains unchanged throughout the reaction. In the example:

• Total initial mass = Mass of potassium + Mass of chlorine = 1.446 g + 8.178 g = 9.624 g
• Total mass of products and unreacted substances = Mass of KCl + Mass of unreacted chlorine = 2.757 g + 6.867 g = 9.624 g

This confirms that mass is conserved, ensuring the calculations align with this fundamental chemical law. Understanding mass conservation helps in balancing chemical equations and predicting the amounts of products formed.

Potassium Chloride

Potassium chloride ( KCl ) is the compound produced in the exercise. This substance forms when potassium and chlorine react:

• It is an ionic compound, consisting primarily of potassium ions ( K^+ ) and chloride ions ( Cl^- ).
• It is commonly used in agriculture and medicine.

Potassium chloride has a crystalline structure and dissolves easily in water. When solving for the amount of KCl formed, understanding chemical formulas and stoichiometry is crucial, as these guide how reactants combine to form products.