Investigate Temperature Change During a Neutralization Reaction

Investigate temperature change during a neutralization reaction

Introduction:
When an alkali neutralizes an acid, a salt and water are formed. Aqueous hydrogen ions (H+(aq)) from the acid react with the hydroxide ions (OH-(aq)) from the alkali, forming water. For hydrochloric acid and sodium hydroxide:
H+(aq) + Cl-(aq) + Na+(aq) + OH-(aq) → Na+(aq) + Cl-(aq) + H2O(l)
Hydrochloric acid
Hydrochloric acid

Sodium Chloride
Sodium Chloride
Sodium Hydroxide
Sodium Hydroxide

Neutralization is an exothermic reaction which means it gives out energy to the surroundings in the form of heat. There’s only a chemical reaction occurring between H+ and OH- ions as the Na+ and Cl- ions in the product is uncharged
H+(aq) + OH-(aq) → H2O(l)
The combination of H+ and OH- ions in this way releases heat energy. The aim of this experiment is to measure the temperature changes during the reaction between hydrochloric acid and sodium hydroxide solution.
Research question:
What happen to the temperature of the solution when using different concentration of acid?
Hypothesis:
Since the volume is kept constant and when the concentration of the acid increases, the acid particles also increase. So the concentration will be directly proportional to the temperature change.
Because neutralization is an exothermic reaction, during the reaction, the temperature will increase until the point of neutralization (at which point the temperature is at its highest), and after this point, the temperature will start to decrease.
My hypothesis is as long as we increase the concentration of acid, the temperature of solution is increased due to more acid particle moving in the solution and cause heat loss.

Apparatus: * Burette 0.5 * Ring stand and ring clamp * Measuring cylinder 0.5 * Data logger and Temperature sensor * Beaker 1.0 * Stirring rod * Safety goggle

Chemical: * Hydrochloric Acid (HCl) 3M, 2.5M, 2M, 1.5M, 1M * Sodium Hydroxide (NaOH) 1M

Independent variable: * Concentration of Hydrochloric Acid / M

Dependent variable: * The average temperature / °C

Factors to control: * Volume: * Volume of NaOH in the beaker should be exactly 25ml * Volume of HCl in the burette should be exactly 50ml * Why to control it: Different volume will cause to inaccuracy result as the rate of reaction will change * How to control it: Use measuring cylinder to make sure we have the exact amount that we need

* Temperature: * Temperature of the atmosphere must be in constant throughout the experiment * Why to control it: Temperature can also change the rate of reaction so the result for each trial would not be accurate * How to control it: Set the air conditioner in the same temperature during the experiment

Procedure:
My teacher only provide 3M and 2M of hydrochloric acid, 2M of sodium hydroxide so I have to dilute from 3M acid to 2.5M, 1.5M, 1M acid; 2M of alkali to 1M.
By using this formula MiVi = MfVf we can define the amount of water is needed to dilute.

Dilute acid to 2.5M
3M x 50ml = 2.5M x Vf 150 = 2.5M x 60ml 60ml – 50ml = 10ml of water

Dilute acid to 1.5M
3M x 50ml = 1.5M x Vf 150 = 1.5M x 100ml 100ml – 50ml = 50ml of water
Dilute acid to 1.0M
2M x 50ml = 1.0 M x Vf 100 = 1.0M x 100ml 100ml – 50ml = 50ml of water
Dilute alkali to 1M
2M x 25ml = 1.0M x Vf 50 = 1.0M x 50ml 50ml – 25ml = 25ml of water

Use the measuring cylinder to place 25ml of 1M NaOH into the beaker.
Place the beaker under the nozzle of the burette so that when HCl drops from the burette it doesn't spill out.
Using measuring cylinder to place 50ml of 1M HCl into the burette
Fix the burette on the stand.
Attach the temperature sensor to connect to the data logger by the ring clamp in
Put the temperature sensor in the solutions in order to measure the temperature change.
From the burette, run in 5ml HCl and stirring the solution with a stirring rod.
Repeat step adding 5cm3 of acid and measuring the temperature until the burette is empty.
Record the maximum temperature in the table
Then repeat the whole process, using the same solution (HCl) with different concentrations of 1.5M, 2M, 2.5M and 3M.
Carry out 3 trials for each concentration experiment and average out the temperatures.

Observation:
Hydrochloric acid and sodium hydroxide is colorless at the beginning of the experiment
The beaker is warm up when added acid to sodium hydroxide.
The solution between acid and alkali is colorless

Data collection and processing:
Table 1: The highest temperature of each trial using different concentration acid

Concentration of Hcl / M | Temperature change / °CTrial 1 | Temperature change / °CTrial 2 | Temperature change / °CTrial 3 | Average temperature / °C | 1.0 | 25.7 | 24.8 | 25.1 | 25.2 | 1.5 | 26.4 | 26.1 | 26.7 | 26.4 | 2.0 | 27.4 | 27.6 | 27.3 | 27.4 | 2.5 | 28.5 | 28 | 28.1 | 28.2 | 3.0 | 29.2 | 28.9 | 29.3 | 29.1 |

Graph: The average temperature of different concentration

Conclusion:
The graph is steadily with a straight line go up, overall it supported my hypothesis. As we change the concentration of the acid the temperature of solution increases. From this I can conclude that concentration will be directly proportional to temperature change