To measure something in enthalpy units, use a calorimeter to measure the change of the heat in a chemical reaction. Add chemicals to the calorimeter's constant pressure system.
- Prepare the calorimeter
Clean the calorimeter, and dry it well. Weigh the empty calorimeter on a scale. Put 10 centimeters of magnesium ribbon in the calorimeter, and weigh it again. Take the mass to 0.001 grams.
- Measure the hydrogen chloride
Pour 50 centimeters-cubed into a cylinder. Find the temperature once every minute for four minutes.
- Add the hydrogen chloride to the calorimeter
Pour the hydrogen chloride into the calorimeter, and shut the lid. Stir the mixture constantly. Drop the thermometer in the calorimeter every 30 seconds for seven minutes. Record each temperature on a sheet of paper.
- Graph the temperatures
Plot the changes in temperature over time from the start of the experiment to the final temperature calculation.
- Calculate the enthalpy
Solve the equation Q = M.HCl C.HCl(Tf - Ti), where (C.HCl = 4.00JK ^ -1 x g ^ -1). The Q in the equation stands for the heat required to change the temperature of the substance. Tf stands for the first recorded temperature. Ti stands for the final recorded temperature. Plug the variable numbers into the equation. Convert the variables to kilojoules per mole. The answer represents the enthalpy units of the temperature changes of the substance.