Chem

Chemistry Coursework

Investigation: To investigate how much energy is transferred as heat when an acid reacts with an alkali.   The acid that I will be using is Sulphuric Acid and the alkali that I will be using is Sodium Hydroxide.

Introduction: Chemical reactions often involve changes in energy. When an acid reacts with an alkali, the energy change is called heat of neutralisation. Heat of neutralisation is the heat released when one mole of water is formed from neutralisation between one mole of hydrogen ions, H+, from an acid and one mole of hydroxide ions, OH- , from an alkali. For example, Sodium Hydroxide and hydrochloric acid react to produce a salt (sodium chloride) and water.

Na+(aq) + OH – (aq) + H+(aq) + Cl-(aq)   Na+(aq) + Cl-(aq) + H2O (l)

During a neutralisation reaction the hydrogen ions from an acid react with hydroxide ions from the alkali to make water:    

                      H+(aq) + OH-   (aq)   H2O (l)  

The remaining ions in the solution make a salt.

You can calculate the energy change of the reaction using the formula:
       
                  Energy change (J) = m x s x t

Where   m = the volume of liquid in the reaction mixture in cm3
                      (Assuming 1 cm3 of the reaction mixture has a mass of 1g)
                s = the specific heat capacity of water (4.2 j/g °C)
                t = the change in temperature in °C

Endothermic reactions take in energy from its surroundings. The energy is usually transferred as heat energy, from the system (reaction mixture) to its surroundings (environment). In an endothermic reaction the temperature of the surroundings (environment) decreases and the temperature of the system (reaction mixture) increases. The temperature change can be measured using a thermometer. Some examples of endothermic reactions are:

  * Electrolysis
  * The reaction between ethanoic and sodium carbonate
CaCo3 + 2CH3COOH   H2O + CO2 + (CH3COO) 2Ca
  * The...