Chemical Equations and the Law of Conservation of Mass

Oct 13, 2025 by wbrum.org 6 views

The law of conservation of mass is a fundamental principle in chemistry that states that matter cannot be created or destroyed in a chemical reaction. This means that the total mass of the reactants must be equal to the total mass of the products. In this article, we will explore which chemical equation models the law of conservation of mass.

What is the Law of Conservation of Mass?

The law of conservation of mass is a fundamental principle in chemistry that states that matter cannot be created or destroyed in a chemical reaction. This means that the total mass of the reactants must be equal to the total mass of the products. The law of conservation of mass is often expressed as:

m (reactants) = m (products)

where m represents the mass of the reactants and products.

Chemical Equations and the Law of Conservation of Mass

Chemical equations are used to represent the reactants and products of a chemical reaction. A chemical equation consists of the reactants on the left-hand side and the products on the right-hand side, separated by an arrow. The law of conservation of mass requires that the total mass of the reactants must be equal to the total mass of the products.

Analyzing the Chemical Equations

Let's analyze the four chemical equations given in the options:

A. $KOH + H_3PO_4 \rightarrow K_3PO_4 + H_2O$

In this equation, the reactants are potassium hydroxide (KOH) and phosphoric acid (H3PO4), and the products are potassium phosphate (K3PO4) and water (H2O). The total mass of the reactants is:

1 mole of KOH = 56.11 g/mol
1 mole of H3PO4 = 98.00 g/mol
Total mass of reactants = 56.11 g/mol + 98.00 g/mol = 154.11 g/mol

The total mass of the products is:

1 mole of K3PO4 = 212.27 g/mol
1 mole of H2O = 18.02 g/mol
Total mass of products = 212.27 g/mol + 18.02 g/mol = 230.29 g/mol

The total mass of the reactants is not equal to the total mass of the products, so this equation does not model the law of conservation of mass.

B. $3KOH + H_3PO_4 \rightarrow K_3PO_4 + 3H_2O$

In this equation, the reactants are 3 moles of potassium hydroxide (KOH) and 1 mole of phosphoric acid (H3PO4), and the products are 1 mole of potassium phosphate (K3PO4) and 3 moles of water (H2O). The total mass of the reactants is:

3 moles of KOH = 3 x 56.11 g/mol = 168.33 g/mol
1 mole of H3PO4 = 98.00 g/mol
Total mass of reactants = 168.33 g/mol + 98.00 g/mol = 266.33 g/mol

The total mass of the products is:

1 mole of K3PO4 = 212.27 g/mol
3 moles of H2O = 3 x 18.02 g/mol = 54.06 g/mol
Total mass of products = 212.27 g/mol + 54.06 g/mol = 266.33 g/mol

The total mass of the reactants is equal to the total mass of the products, so this equation models the law of conservation of mass.

C. $2KOH + H_3PO_4 \rightarrow K_3PO_4 + 2H_2O$

In this equation, the reactants are 2 moles of potassium hydroxide (KOH) and 1 mole of phosphoric acid (H3PO4), and the products are 1 mole of potassium phosphate (K3PO4) and 2 moles of water (H2O). The total mass of the reactants is:

2 moles of KOH = 2 x 56.11 g/mol = 112.22 g/mol
1 mole of H3PO4 = 98.00 g/mol
Total mass of reactants = 112.22 g/mol + 98.00 g/mol = 210.22 g/mol

The total mass of the products is:

1 mole of K3PO4 = 212.27 g/mol
2 moles of H2O = 2 x 18.02 g/mol = 36.04 g/mol
Total mass of products = 212.27 g/mol + 36.04 g/mol = 248.31 g/mol

The total mass of the reactants is not equal to the total mass of the products, so this equation does not model the law of conservation of mass.

D. $3KOH + H_3PO_4 \rightarrow K_3PO_4 + 2H_2O$

In this equation, the reactants are 3 moles of potassium hydroxide (KOH) and 1 mole of phosphoric acid (H3PO4), and the products are 1 mole of potassium phosphate (K3PO4) and 2 moles of water (H2O). The total mass of the reactants is:

3 moles of KOH = 3 x 56.11 g/mol = 168.33 g/mol
1 mole of H3PO4 = 98.00 g/mol
Total mass of reactants = 168.33 g/mol + 98.00 g/mol = 266.33 g/mol

The total mass of the products is:

1 mole of K3PO4 = 212.27 g/mol
2 moles of H2O = 2 x 18.02 g/mol = 36.04 g/mol
Total mass of products = 212.27 g/mol + 36.04 g/mol = 248.31 g/mol

The total mass of the reactants is not equal to the total mass of the products, so this equation does not model the law of conservation of mass.

Conclusion

In conclusion, the chemical equation that models the law of conservation of mass is:

B. $3KOH + H_3PO_4 \rightarrow K_3PO_4 + 3H_2O$

The law of conservation of mass is a fundamental principle in chemistry that states that matter cannot be created or destroyed in a chemical reaction. In our previous article, we explored which chemical equation models the law of conservation of mass. In this article, we will answer some frequently asked questions about the law of conservation of mass.

Q: What is the law of conservation of mass?

A: The law of conservation of mass is a fundamental principle in chemistry that states that matter cannot be created or destroyed in a chemical reaction. This means that the total mass of the reactants must be equal to the total mass of the products.

Q: Why is the law of conservation of mass important?

A: The law of conservation of mass is important because it helps us understand the behavior of matter in chemical reactions. It ensures that the total mass of the reactants is equal to the total mass of the products, which is a fundamental principle of chemistry.

Q: How does the law of conservation of mass relate to the law of conservation of energy?

A: The law of conservation of mass and the law of conservation of energy are two separate principles in chemistry. The law of conservation of mass states that matter cannot be created or destroyed in a chemical reaction, while the law of conservation of energy states that energy cannot be created or destroyed in a chemical reaction, only converted from one form to another.

Q: Can the law of conservation of mass be broken?

A: No, the law of conservation of mass cannot be broken. It is a fundamental principle of chemistry that has been consistently observed and verified through numerous experiments and observations.

Q: What are some examples of the law of conservation of mass in everyday life?

A: The law of conservation of mass is observed in many everyday situations, such as:

When you burn a piece of wood, the mass of the wood is converted into the mass of the ash and the gases released.
When you mix two substances together, the total mass of the mixture is equal to the total mass of the individual substances.
When you cook a meal, the mass of the ingredients is converted into the mass of the cooked food.

Q: How can the law of conservation of mass be applied in chemistry?

A: The law of conservation of mass can be applied in chemistry in many ways, such as:

Balancing chemical equations to ensure that the total mass of the reactants is equal to the total mass of the products.
Calculating the mass of reactants and products in a chemical reaction.
Understanding the behavior of matter in chemical reactions.

Q: What are some common misconceptions about the law of conservation of mass?

A: Some common misconceptions about the law of conservation of mass include:

Thinking that matter can be created or destroyed in a chemical reaction.
Believing that the law of conservation of mass only applies to certain types of chemical reactions.
Assuming that the law of conservation of mass is not important in everyday life.

Conclusion

In conclusion, the law of conservation of mass is a fundamental principle in chemistry that states that matter cannot be created or destroyed in a chemical reaction. It is an important concept that has been consistently observed and verified through numerous experiments and observations. By understanding the law of conservation of mass, we can better understand the behavior of matter in chemical reactions and apply this knowledge in many areas of chemistry.

Frequently Asked Questions

Q: What is the law of conservation of mass?
A: The law of conservation of mass is a fundamental principle in chemistry that states that matter cannot be created or destroyed in a chemical reaction.
Q: Why is the law of conservation of mass important?
A: The law of conservation of mass is important because it helps us understand the behavior of matter in chemical reactions.
Q: Can the law of conservation of mass be broken?
A: No, the law of conservation of mass cannot be broken.
Q: What are some examples of the law of conservation of mass in everyday life?
A: The law of conservation of mass is observed in many everyday situations, such as burning a piece of wood, mixing two substances together, and cooking a meal.
Q: How can the law of conservation of mass be applied in chemistry?
A: The law of conservation of mass can be applied in chemistry in many ways, such as balancing chemical equations, calculating the mass of reactants and products, and understanding the behavior of matter in chemical reactions.