Title: Thermometric Titration
Date: 2024/01/14
Aim: To determine the end point of the thermometric titration between hydrochloric acid and
sodium hydroxide.
Materials and Apparatus:
Materials: Hydrochloric acid, Sodium hydroxide
Apparatus: Burette, 25cm³ measuring cylinder, Mercury, Thermometer, Plastic cup
Method: The experiment was initiated by filling a clean burette with the supplied hydrochloric
acid. Carefully, 25.0 cm³ of the 2.0M sodium hydroxide solution was measured using a 25 cm³
pipette and transferred to a clean plastic cup. Before proceeding with the temperature
measurements, the thermometer was checked to ensure familiarity with its scale graduations.
The thermometer was also inspected to verify the presence of a continuous, unbroken thread of
mercury. The initial temperature of the sodium hydroxide solution was then measured by placing
the bulb of the thermometer in the solution and monitoring the temperature over a two-minute
period. Once a steady temperature was reached, it was recorded as the initial temperature. With
the thermometer kept in the cup, successive 5 cm³ portions of the hydrochloric acid were added
to the solution. After each addition, the mixture was thoroughly stirred with the thermometer, and
the highest temperature reached after stirring was recorded. This process continued until three
successive temperature readings either fell or remained unchanged.All temperature readings
were recorded in an appropriate table of results. Subsequently, a graph of temperature (y-axis)
against the volume of acid added (x-axis) was plotted. Two best-fit straight lines were drawn
through the two sets of points on the graph. Finally, the endpoint of the titration was determined
from the point of intersection of the lines on the graph. This represented the volume of acid
required to completely neutralize the sodium hydroxide solution.
Results:
Table of volume and temperature readings:
Volume of 0 5 10 15 20 25 30 35
acid
added/cm3
Temperature 30 34.1 36.9 38.2 39.9 38 36.2 35
/𝐷𝑒𝑔𝑟𝑒𝑒𝑠 𝐶
Treatment of results:
1.Write a balanced equations for the reaction between the acid and alkali
2NaOH+HSO4—>Na2SO4+2H2O
2.Calculate the number of moles of alkali in the 25cm3 measured out
(2.0Mx0.025dm3=0.005moles)
3.
(a)Use the equation in 1 and your answer to 2 to find the number of moles of acid added
by the end point.
(2molNaOH)/40=0.05moles
(1 mol H2SO4)/40=0.025moles
(b)From your answer to (a) find the concentration of acid in moles per dm3
1 mol per dm3
4.Suggest with reason how to find the concentration of the acid by this method compare
with an acid-base titration in which an indicator is used.
To find the concentration of the acid using the method described, one can measure the
temperature change during dissolution and apply calorimetric principles to relate the heat
change to the amount of acid dissolved, thus determining its concentration. Compared to an
acid-base titration with an indicator, this method offers advantages such as precision and
sensitivity, but may require more time and equipment.
5. Use your results in this titration to find the heat of neutralization of hydraulic acid.
0.045kg x 42 x 9.9 degrees Celsius=1.8711 , 1.8711/0.05=37.422kJ
6. Read up the chemistry of Cold packs and hot packs and their use at Sporting events
and field operations for camping, the military,etc. Name at least two substances used in
each type of pack.
Cold packs Hot packs
Ammonium nitrate Magnesium sulfate
Calcium ammonium nitrate Calcium chloride
