Answer to Question #149223 in General Chemistry for cecilia boghossian

Question

if 0,50g of magnesium is reacted with 15 ml of HCl at 0,75M, do you think that the reaction will release more energy and therefore the temperature variation of the environment will be higher? justify your answer by specifying which of the reagents is in excess.

Answer 1

0,50g of magnesium is reacted with;

15 ml of HCl at 0,75M

Magnesium reacts with hydrochloric acid according to the equation:

Mg(s) + 2 HCl(aq) --> MgCl ₂(aq) + H ₂(g)

Mole ratio :

1 : 2 : 1 : 1

Therefore

1 : 2

0.75/2 = 0.375 moles of magnessium

Therefore the  reaction between magnesium metal and hydrochloric acid is exothermic, because it released energy in the form of heat (increase of temperature). The energy required to break the bonds of the reactants were more than the energy required to make the new bonds of the products.