The equation for the reaction of magnesium ribbon and hydrochloric acid is Mg(s) + 2 HCl(aq) → MgCl2(aq) + H2(g)
If 1.53 g magnesium reacted, how many moles of hydrogen gas was produced?
Report your answer to three significant figures.
Mg = 24.3 g/mol

The mole of hydrogen gas that will be produced from the reaction would be 0.0630 moles.

From the equation of the reaction:

The mole ratio of Mg to H2 gas is 1:1. Thus, for every one mole of Mg consumed by the reaction, 1 mole of H2 is produced, all other things being equal.

Recall that: mole = mass/molar mass

1.53 g of magnesium = 1.53/24.3

                                     = 0.0630 mole (to 3 significant figures)

Since the mole ratio of Mg to H2 is 1:1, it means that the number of moles of hydrogen gas produced would also be 0.0630 moles.

More on calculating moles can be found here: link

.063

Explanation:

1.53g Mg * (1 mol Mg/ 24.3 g Mg) * (1 mol H2/1 mol Mg) = .063 mol H2

a. energy is absorbed in the reaction.

if in a given reaction the energy of products is greater than the energy of reactants it means that reaction is endothermic and during the reaction, the energy is absorbed by reactants. in an endothermic reaction, the products have more stored chemical energy than the reactants. and in this reaction the reactants are more stable than products before the compounds with less energy are always more stable.

o conteúdo de calor de um sistema é igual à entalpia apenas para um sistema que é constante