How much energy is transferred as heat when acids react with alkalis?
Acids have a low pH <7
Alkalis have a high pH >7-14
Neutralisation is the reaction between an acid and an alkali base to form a neutral solution. A neutral solution can only be achieved if both the base and acid are of equal strengths. This is due to the H+ ions in the acid reacting with the OH- ions in the alkali, to produce H2O better known as water, which is a neutral substance.
H+ OH- → H2O
However water is not the only substance produced when an acid and an alkali (base) react together, salt is also produced.
When an acid reacts with an alkali it produces a salt and water.
Acid +Alkali Salt + Water + Energy
NaOH+HCl NaCl+H2O (Hydrochloric Acid + Sodium Hydroxide -> Sodium Chloride + Water)
This reaction is called neutralisation. The alkali has neutralised the acid by removing its H+ ions, and turning them into water.
Neutralisation is an exothermic reaction, as a result of this the heat is given out because of the energy released from the forming bonds is greater than that taken in and used in the breaking of the bonds. The heat which gives off in the reaction can be measured by changing it into joules of energy. The heat produced during neutralisation is because of the reaction of acid and alkali to produce 1 mole of water.
In an exothermic reaction the products have a lower energy than the reactants, because energy is lost during the reaction.
* If there is a rise in the temperature, then the reaction is exothermic and involves a negative enthalpy change.
* If there is a decrease in the temperature then the reaction is endothermic and involves a positive enthalpy change.
Reaction that gives out energy to the surrounding is known as exothermic reaction. Examples of these are:
* Neutralisation reaction between acid and alkali
* The reaction between water and calcium oxide
Factors that could...