Answer:
The mass of the products left in the test tube will be less than that of the original reactants.
Explanation
The equation for the reaction is
Mg(s) + 2HCl(aq) → MgCl2(aq) + H2(g)
1.0 3.0 3.9 0.1
Assume you started with 1.0 g of Mg.
It will react with 3.0 g of HCl to form 3.9 g of MgCl2 and 0.1 g of H2
.
Mass of reactants = mass of products
1.0 g + 3.0 g = 3.9 g + 0.1 g
4.0 g = 4.0 g
The Law of Conservation of Mass is obeyed.
However, your test tube and its contents will weigh 0.1 g less than it did before the reaction.
Does that contradict the Law of Conservation of Mass? It does not.
One of the products was the gas, hydrogen, and it escaped from the test tube. You weren't measuring all the products, so test tube and its contents weighed less than before.
The question is incomplete, here is the complete question:
Silicon reacts with carbon dioxide to form silicon carbide and silicon dioxide. Write the balanced chemical equation.
<u>Answer:</u> The balanced chemical equation is written below.
<u>Explanation:</u>
Every balanced chemical equation follows law of conservation of mass.
A balanced chemical equation is defined as the equation in which total number of individual atoms on the reactant side is equal to the total number of individual atoms on product side.
The balanced chemical equation for the reaction of silicon and carbon dioxide follows:

By Stoichiometry of the reaction:
2 moles of silicon reacts with 1 mole of carbon dioxide gas to produce 1 mole of silicon carbide and 1 mole of silicon dioxide
Hence, the balanced chemical equation is written above.
Answer:
H₂ + Cl₂ → 2HCl
Explanation:
The equation that is balanced and follows the law of conservation of mass is:
H₂ + Cl₂ → 2HCl
Based on the law of conservation of mass "in a chemical reaction, matter is neither created nor destroyed but they combine with one another".
It suggests that the number of species on both sides of the expression must be the same.
For the given reaction:
H₂ + Cl₂ → 2HCl
Reactant side Product side
H 2 2
Cl 2 2
The answer is what the other person wrote :)