Question

A 46-g sample of potassium completely reacts with chlorine to form 88 g of potassium chloride. How many grams of chlorine must have reacted?

Answer 1

Calculation: Grams of Chlorine Reacted

Given:

• Mass of potassium (K) = 46 g

• Mass of potassium chloride (KCl) formed = 88 g

Step 1: Use the Law of Conservation of Mass

The total mass of reactants equals the mass of products:

$$\text{Mass of K}+{\text{Mass of Cl}}_2=\text{Mass of KCl}$$$$46\text{g}+{\text{Mass of Cl}}_2=88\text{g}$$

Step 2: Solve for Chlorine Mass

$${\text{Mass of Cl}}_2=88\text{g}-46\text{g}=42\text{g}$$

 Answer:

42 grams of chlorine (Cl₂) must have reacted.

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Why This Works:

• Potassium (K) and chlorine (Cl₂) react in a 1:1 molar ratio to form KCl, but the calculation only requires mass balance—no moles needed!

• Shortcut: Subtract the given mass of K from the total mass of KCl.