Magnesium reacts with hydrochloric acid to produce hydrogen gas. ΔH°f for HCl(aq) = –167.16 kJ/mol ΔH°f for MgCl2(aq) = –801.17 kJ/mol (i) Calculate the standard enthalpy change for this reaction. (ii) For this reaction, explain the sign of ΔT for the surroundings (iii) Write the net ionic equation for this reaction
Thermochemistry
Thermochemistry can be considered as a branch of thermodynamics that deals with the connections between warmth, work, and various types of energy, formed because of different synthetic and actual cycles. Thermochemistry describes the energy changes that occur as a result of reactions or chemical changes in a substance.
Exergonic Reaction
The term exergonic is derived from the Greek word in which ‘ergon’ means work and exergonic means ‘work outside’. Exergonic reactions releases work energy. Exergonic reactions are different from exothermic reactions, the one that releases only heat energy during the course of the reaction. So, exothermic reaction is one type of exergonic reaction. Exergonic reaction releases work energy in different forms like heat, light or sound. For example, a glow stick releases light making that an exergonic reaction and not an exothermic reaction since no heat is released. Even endothermic reactions at very high temperature are exergonic.
(a) Magnesium reacts with hydrochloric acid to produce hydrogen gas.
ΔH°f for HCl(aq) = –167.16 kJ/mol
ΔH°f for MgCl2(aq) = –801.17 kJ/mol
(i) Calculate the standard enthalpy change for this reaction.
(ii) For this reaction, explain the sign of ΔT for the surroundings
(iii) Write the net ionic equation for this reaction
(iv) What type of reaction is this?
(v) In our everyday lives, we observe what happens around us using five biological
senses. Give the names of the biological senses.
(vi) If you reacted magnesium with hydrochloric acid in the laboratory, specifically what
would you observe? Give four observations.
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