Understanding the Importance of Balanced Chemical Equations: A Case Study of 2K2CrO4aq Pb(NO3)2aq → 2KNO3aq PbCrO4sdownarrow

The concept of a balanced chemical equation is fundamental in chemistry, as it ensures the conservation of mass and charge. Without a balanced equation, one is not following the rules of chemistry but engaging in what might be humorously referred to as ldquo;witchcraftrdquo;. This article will examine a particular chemical equation to illustrate these principles.

Introduction to the Chemical Equation in Question

Letrsquo;s consider the following equation:

2K2CrO4aq Pb(NO3)2aq → 2KNO3aq PbCrO4sdownarrow

At first glance, this equation might seem correct, but upon closer inspection, it fails to meet the criteria of a balanced equation. Itrsquo;s crucial to verify both the conservation of mass and charge.

Assessing the Conservation of Mass and Charge

Title: Assessing the Conservation of Mass and Charge

Mass and charge are conserved in a chemical reaction. If the equation does not reflect this principle, it is not a balanced equation. Letrsquo;s break down the given equation to see if it complies with these principles.

Mass Conservation

Courtesy of the law of conservation of mass, the total mass of reactants must equal the total mass of products. In the given equation, we need to count the moles of each element to ensure balance.

Reactants: 2 moles of K (from 2K2CrO4) 2 moles of Cr (from 2K2CrO4) 8 moles of O (from 2K2CrO4) and 2 nitrogen (N) atoms from Pb(NO3)2 4 moles of Pb (from Pb(NO3)2) Products: 4 moles of K (from 2KNO3) 2 moles of Cr (from PbCrO4) 6 moles of O (from 2KNO3) 4 moles of Pb (from PbCrO4) 2 nitrogen (N) atoms from 2KNO3

Upon reviewing the reactants and products, it is evident that the equation does not balance with respect to the moles of potassium (K), chromium (Cr), and oxygen (O).

Charge Conservation

Charge is also conserved in a chemical reaction, meaning the total positive charge must equal the total negative charge on both sides of the equation. Letrsquo;s analyze the charges.

Reactants: 2 moles of K (1 total charge from 2K2CrO4) 2 moles of CrO42- (2- total charge from 2K2CrO4) 2 moles of Pb2 (2 total charge from Pb(NO3)2) Products: 4 moles of K (1 each from 2KNO3) 1 mole of CrO42- (2- from PbCrO4) 4 moles of Pb(NO3)2 produces 8 moles of NO3- (1- each, totaling 8-)

The charge is not balanced on the product side because there is an excess of -1 charge from the nitrate ions (NO3-) in the reactants.

Correcting the Equation

To correct this equation, we need to adjust the coefficients so that both mass and charge are conserved. Letrsquo;s start by ensuring the charge is balanced. The simplest way to achieve this is to balance the equation by adjusting the coefficients of the reactants and products appropriately.

By multiplying K2CrO4 by 2 and removing the 2 in front of Pb(NO3)2, we get:

K2CrO4aq Pb(NO3)2aq → 2KNO3aq PbCrO4sdownarrow

Now letrsquo;s verify the balance:

Mass Balance

Reactants: 1 mole of K2CrO4 (2 moles of K, 1 mole of Cr, and 4 moles of O, plus 2 nitrogen atoms) 1 mole of Pb(NO3)2 (1 mole of Pb, 2 nitrogen atoms, and 6 moles of O) Products: 2 moles of KNO3 (2 moles of K, 2 moles of NO3-) 1 mole of PbCrO4 (1 mole of Pb, 1 mole of Cr, and 4 moles of O)

Both sides are now balanced with respect to mass.

Charge Balance

Reactants: 2 moles of K (from 1K2CrO4) 2 moles of CrO42- (from 1K2CrO4) 2 moles of Pb2 (from 1Pb(NO3)2) Products: 2 moles of K (from 2KNO3) 2 moles of NO3- (from 2KNO3) 1 mole of CrO42- (from PbCrO4) 1 mole of Pb2 (from PbCrO4)

The charges are balanced on both sides, confirming that the equation is now correct.

Conclusion

A balanced chemical equation is essential for accurately representing a chemical reaction. The correct balanced equation for the given scenario is: