# How does stoichiometry support the law of conservation of mass?

Stoichiometry is a concept based on balanced chemical equation and stoichiometry can support the law of conservation of mass.

We’ve discovered that in balanced chemical equation, the mass of reactants and products remain the same.

## What is law of conservation of mass?

Law of conservation of mass is otherwise called the law of conservation of matter and it states that matter cannot be created nor destroyed 8but can be transformed from one form to another.

So, it implies that in every balanced chemical equation, the mass of reactants and products remains the same (or equal)

Recall that we emphasized earlier that stoichiometry is based on the concept of calculations involving quantities of reactants and products from balanced chemical equation.

Since law of conservation of mass deals with mass of reactants before reaction equaling mass of products after reaction and this is simply illustrated by a balanced chemical equation.

A balanced chemical equation is the basis and foundation of stoichiometry.

So, when we ask how stoichiometry support law of conservation of mass does, we are trying to

find out the relationship between stoichiometry and law of conservation of mass.

I will prove how stoichiometry supports law of conservation of mass via two ways

a. By experiment

b. By theoretical approach

1. By experiment

We can prove how stoichiometry supports the law of conservation of mass using a simple experiment.

From the experimental set up, you’ll notice that the mass of the reactants before reaction equals the mass of products after reaction

This is verified by the weight (mass) shown by the weighing balance.

So, since the mass (quantity of matter) of the reactants and products do not change, the law of

conservation of matter or mass is verified.

Second example is having like 40.6 grams of iron and Sulphur to still form 40.6 grams of iron II sulphide.

Fe + S === FeS

From this experiment, the mass of reactants before reaction started was weighed and we got 40.6 grams. After the reaction, the products formed were weighed and we got same mass.

This proves that stoichiometry supports law of conservation of mass since mass (or matter)  remained the same but only was transformed from one from one form to another..

## How do you verify the law of conservation of mass using stoichiometry?

As I said earlier, law of conservation of mass can be illustrated theoretically.

Example 1

Check if the equation verifies the law of conservation of mass

H2 + Cl2==2HCl

Solution

I will theoretically calculate the mass of the reactants and products.

Reactants

H2= 1 x2 = 2 g

Cl2 = 35.5 X 2= 71 g

Total = 73 grams

Products

36.5 x2 = 73 grams

So theoretically we have same mass of reactants and products.

Example 2

Verify that this equation supports law of conservation of matter

Mg + 2HCl == MgCl2 + H2

Solution

For reactants

Mg

24g

2HCl

2 (1 +35.5) = 73 g

Total

24 + 73 = 97 grams

For Products

MgCl2

24 +35.5 ×2 = 24 + 71 =95 grams

H2

1x 2 = 2 grams

Total

97 grams

So we you compare the two masses, they are the same and thus the law of conservation of matter is

verified

Example 3

Show that the equation verifies the law of conservation of mass

2Na + 2H2O === 2NaOH + H2

Solution

For reactants

Na

2 x 23 = 46 g

2H2

2 (1 x 2+16) = 2 (18) = 36 g

Total = 82 grams of the reactants

For Products

2NaOH

2(23+16+1) = 2 x 40 = 80 g

H2

1 x 2 = 2 g

Mass of products = 82 g

The law is thus verified by having same mass of reactants and products

Example 4

Verify if the decomposition of calcium carbonate supports the law of conservation of matter.

CaCO3 === CaO + CO2

Solution

Reactants

CaCO3

40+ 12+ 16x 3 = 100g

Products

CaO

40+ 16 = 56 g

CO2

12 + 16 x 2 = 12 +32 = 44 grams

Total = 56 g + 44 g = 100 g

Example 5

Finally let’s show how the formation of ammonia could be used to verify the law of conservation of matter.

N2+ 3H2 ===2NH3

Solution

Reactants

N2 and 3H2

N2 = 14x 2= 28 g

3H2 = 3(1 x 2) = 6 g

Total = 34 grams of the reactants

Products

2NH3= 2 (14 + 1 x 3) = 2 (17) = 34 grams of the products

All these examples prove how stoichiometry support law of conservation of matter