# Research question: how to convert NaOH to NaCl by two different routes , and measure the enthalpy changes for each one in order to test Hesss law ?

by lolitamatti (student)

Name: Rand Ishaq

School: katedralskolan         chemistry IA        2011-12-17

converting NaOH to NaCl by two different routes , and measuring the enthalpy changes for each one in order to test Hess’s law .

aim: the aim is to measure and compare the quantity of heat involved in three reactions and to provide experimental verification of Hess's Law

research question:  how to convert NaOH to NaCl by two different routes , and measure the enthalpy changes for each one in order to test Hess’s law ?

general background:

The foundation of the study of thermochemistry was laid by the chemist Germain Hess, who investigated heat in chemical reactions during the last century. One statement of the law that bears Hess's name says:

The enthalpy change for any reaction depends on the products and reactants and is independent of the pathway or the number of steps between the reactant and product

In this experiment, the enthalpy of several reactions will be determined using the method of calorimetry.

The reactions that will be considered are the following:

1: NaOH (aq) + HCl (aq)             NaCl (aq) + H2O (l)

All of the reactions in this experiment are exothermic. As heat is given off for each reaction, the temperature of the mixture will increase. The amount of heat given off by the reaction can be calculated according to the following equation:

q= mcΔT

Where: m = mass (g)

c = specific heat capacity (The specific heat capacity of each mixture can be approximated as that of water, 4.18 J/g ºC.)

ΔT = the change in temperature (ºC)

Given the volume and concentration of each solution, the number of moles for each substance in the reaction can be calculated, therefore, the enthalpy of each reaction can be calculated in

materials needed :

•  ( 8.0 grams )sodium hydroxide, NaOH
• labQuest
•  2 graduated cylinders of size( 100 mL ± 0.5)
•  (100 cm3) 2 M Hydrochloric acid solution ,HCL
• Measuring pipette (25cm3)
• glass stir stick
• mortar
• scale
• cupcake paper form
• thermos
• (100 cm3 ) of water H2O

Method:

Route (A):

1. 4.0 g of sodium hydroxide is granted using the mortar into powder
2.  50.0 cm3water is measured using measuring cylinder and then it is poured into the thermos.
3.  The lab-quest was set to start the  recording of the temperature of the water.
4. A solution of  sodium hydroxide is made by adding 4.0 g sodium hydroxide to the  of water in the thermous.

1. Temperature is collected  every 30 seconds until it reaches the original temperature
2. 50.00 cm3 of  HCl is added to the solution.
3. Temperature of the solution is collected each 30 seconds  .
4.  The end product will be 100.0 cm3 of NaCl with the concentration of 1 mol dm-3

Route (B):

1. 4.0 g of sodium hydroxide is granted using the mortar into powder
2. 50.00 cm3HCl is measured using  measuring  pipette and then it is poured  into the thermos .
3.  the lab-quest was set to start the recording of the temperature of the HCl.
4.  4.0 g of the granted sodium hydroxide is poured into the HCl in the thermos .

1. Temperature is collected every 30 seconds until it reaches the original temperature.

1. The solution is diluted by  of water.
2. Temperature is collected every 30 seconds for 3 minutes
3. The end product will be 100.0 cm3 of NaCl with the concentration of 1 mol dm-3

data collection and processing

50.00cm3                     H1

NaOH (s), 2M HCl (aq)                                                   2M NaCl (aq)

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