Which chemical equation below is balanced to correctly represent the Law of Conservation of Mass?

The 3rd equation.

Cl2 + 2NaBr —> 2NaCl + Br2

Explanation:

The law of conservation of matter (mass) states that matter can neither be created nor destroyed during a chemical reaction but can be transferred from one form to another. This implies that unbalanced chemical equation shows that matter (mass) has been created or destroyed.

Now, we shall determine which equation is balanced as follow:

1. 2Cl2 + NaBr —> 2NaCl + Br2

Reactant >>>>>>>> Product

4 Cl >>>>>>>>>>>> 2 Cl

1 Na >>>>>>>>>>>> 2 Na

1 Br >>>>>>>>>>>> 2 Br

Thus, the equation is not balanced.

2. Cl2 + NaBr —> NaCl + Br2

Reactant >>>>>>>> Product

2 Cl >>>>>>>>>>>> 1 Cl

1 Na >>>>>>>>>>>> 1 Na

1 Br >>>>>>>>>>>> 2 Br

Thus, the equation is not balanced.

3. Cl2 + 2NaBr —> 2NaCl + Br2

Reactant >>>>>>>> Product

2 Cl >>>>>>>>>>>> 2 Cl

2 Na >>>>>>>>>>> 2 Na

2 Br >>>>>>>>>>>> 2 Br

Thus, the equation is balanced.

From the illustration made above only the 3rd equation is balanced. And this is in line with the law of the Conservation of matter (mass) as matter (mass) was not created nor destroyed during the chemical reaction but was transferred to other forms.

answer is: c. the experiment shows that the red substance experienced a chemical change.

this is chemical change (chemical reaction), because two new substances are formed (metalig liquid and gas), the atoms are rearranged and the reaction is followed by an energy change.

this is example of chemical decomposition.

chemical decomposition (analysis) is the separation of a single chemical compound into its two or more elemental parts or to simpler compounds.  

chemical decomposition is opposite of chemical synthesis.

in scientific notation, the value of the  speed of light in a vacuum

  will be written as 2.995 * 10^8. when this value is represented in the form of

  a * 10^b, then, a = 2.995 and b = 8.

the value of the speed of light in a vacuum given above can also be rounded up to approximately 300000000. in this case, the scientific notation will be written as 3 *10^8.