how does the law of conservation of mass apply this reaction mg + HCl -- H2 + mgcl2
A: equation needs to be balanced or if you were hydrogen atoms in the equation than magnesium or chlorine
B: the law of conservation of mass has already been applied there is an equal number of each element on both sides of the equation
C: only hydrogen needs to be a balance there are equal numbers of magnesium and chloride
D: hydrogen and chlorine need to be balanced there's an equal amount of magnesium on each side

The correct answer is D hydrogen and chlorine need to be balanced there's an equal amount of magnesium on each side. I just took the test and got the correct answer.

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BarrettArcher BarrettArcher · Answer 2 · 2018-10-30T08:00:16-04:00

Answer : The correct answer is (D).

Explanation :

Law of conservation of mass : In a chemical reaction, the mass of reactants must be equal to the mass of products.

The given chemical reaction is,

\(Mg+HCl\rightarrow H_2+MgCl_2\)

According to the reaction,

The mass of reactant = Mass of Mg + Mass of HCl = 24.3 + 36.5 = 60.8 g

The mass of product = Mass of \(H_2\) + Mass of \(MgCl_2\) = 2 + 95.2 = 97.2 g

From this we conclude that the mass of reactant are not equal to the mass of product. So, it does not follow the law of conservation of mass.

So, First we will balance the above chemical reaction. The hydrogen and chlorine need to be balanced.

The Net balanced chemical reaction is,

\(Mg+2HCl\rightarrow H_2+MgCl_2\)

According to the reaction,

The mass of reactant = Mass of Mg + Mass of 2(HCl) = 24.3 + 2(36.5) = 97.3 g

The mass of product = Mass of \(H_2\) + Mass of \(MgCl_2\) = 2 + 95.2 = 97.2 g

From this we conclude that the mass of reactant are equal to the mass of product. So, it follows the law of conservation of mass.

Hence, the hydrogen and chlorine need to be balanced so that there's an equal amount of magnesium present on each side of the given chemical reaction.