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Lab report Determination of Enthalpy Change of Neutralization

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Introduction

Experiment 7 Determination of Enthalpy Change of Neutralization Aim, introduction, apparatus and procedures refer to the instruction sheet. Risk Assessments The thermometer used in the experiment is neither made up of alcohol or mercury. Both substances are harmful to our human body. Alcohol will catch fire quickly when it is in contact with fire or any flammable substance. Mercury is a poisonous and extremely toxic chemical. It can cause both chronic and acute poisoning. As a result, we must handle or use the thermometer carefully. Don't use the thermometer as the gas rod to stir the solution. If the mercury or alcohol is spilt out from the thermometer, we must leave the area of alcohol or mercury and then call the teacher immediately as we don't know how to clean the mercury or alcohol at our level. Secondly, hydrochloric acid used in the experiment is corrosive although it is diluted. It can hurt our skin and irritate our eyes. Therefore, we should handle it very carefully. If the acid is spiller out and fell on our skin or eyes, we have to wash the infected area with plenty of running water or eye wash bottle. Moreover, the hydrogen gas produced from the reaction between calcium and hydrochloric acid is flammable. Explosion will occur if there is fire. As a result, we should keep the experiment away from the fire and conduct the experiment under the good ventilation condition. Results & Calculations Time (s) / Temperature ( ) ...read more.

Middle

/1000 = 0.05 Kg Heat given out = (0.05 * 4200 + (3/29 * 0.02073 + 3/26 * 0.02234) * 840) * 13.5 = 2888.667227J HCl (aq) + NaOH (aq) � NaCl (aq) + H2O (l) No of mole of NaOH = 4 * 0.025 = 0.1 mol According to the equation, 1 mole of H2SO4 reacts with 2 mole of NaOH to form 2 mole of H2O. So, No of mole of H2O = 0.1 mol Heat given out per mole of H2O formed = 2888.667227 / 0.1 = 28.9 KJ mol-1 The enthalpy change of neutralization is -28.9 KJ mol-1 Discussion In the experiment and calculation, there are several assumptions. Firstly, we assume that there is no heat loss to the surroundings and the experiment was implemented under room condition. In addition, heat capacity of the apparatus was negligible and the specific heat capacity of the product solution is 4200 J Kg-1 K-1. Moreover, we assume 1 g of the solution equals to 1 ml of the solution. Several sources of error are in the experiment and we can improve the experiment from such errors. At first, as the temperature of solution recorded by thermometer was increased quickly, it is difficult for us to use human eyes to get the temperature. As a result, the maximum temperature we got may be different from the actual one. So the enthalpy changes of the formation of the substances are inaccurate. To avoid such error, we can prepare a data-logger system connected with computer to record the temperature change of the solution. ...read more.

Conclusion

While neutralization between 2.0M of sulphuric acid and 4.0M of sodium hydroxide is a complete reaction because the mole ratio is 1: 2. As a result the temperature increased of neutralization between 2.0M of sulphuric acid and 4.0M of sodium hydroxide is much higher than that of neutralization between 2.0M of sulphuric acid and 2.0Mof sodium hydroxide. Q14 The temperature increased of neutralization between 2.0M of hydrochloric acid and 2.0Mof sodium hydroxide is much lower than that between 2.0M of sulphuric acid and 4.0M of sodium hydroxide due to the difference of no of mole of hydrogen dissociated in the solution. As sulphuric acid is dibasic acid while hydrochloric acid is monobasic acid. As a result, the amount of hydrogen ionized by the sulphuric acid is higher than that of hydrochloric acid. Furthermore, from the equation, 1 mole of hydrochloric acid reacts with 1 mole of sodium hydroxide. So the neutralization between 2.0M of hydrochloric acid and 4.0M of sodium hydroxide is an incomplete reaction because the mole ratio is 1: 2. While neutralization between 2.0M of sulphuric acid and 4.0M of sodium hydroxide is a complete reaction because the mole ratio is 1: 1. As a result the temperature increased of neutralization between 2.0M of sulphuric acid and 4.0M of sodium hydroxide is much higher than that of neutralization between 2.0M of hydrochloric acid and 2.0Mof sodium hydroxide. Conclusion From the above six neutralization, we can calculate the enthalpy change of neutralization by (m1c1 + m2c2) * Temp. Difference. Through the comparisons between the reaction, we can know about how the effect of concentration, basicity and straightness of acid and base affect the enthalpy change of neutralization. ...read more.

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