calculate enthalpy changes in reactions involving solutions

• what type of reaction? so?

  can be either exothermic or endothermic, the temperature of the solution may increase or decrease during the reaction.
• how do we work out maximum amount of heat energy transferred during the reaction?

  measure initial temp of the water before the reaction begins and add the second reactant then monitor the temp continually as the reaction proceeds.
• set up?


  here

  
• step 1:


  use a measuring cylinder to transfer a specified volume of water or the 1st reactant solution into a polystyrene cup inside a glass beaker to keep it upright,
• step 2:

  measure and record the initial temp of the liquid and start the timer.
• step 3:


  continue to measure and record the temp of the liquid every minute for 3 minutes. Don't stop the timer when taking measurements.
• step 4:


  at the 4th minute add the 2nd reactant to the liquid in the cup but don't measure the temp.
• step 5:


  at the 5th minute, measure and record the temp and do so for every minute up to 10 minutes.
• step 6:


  plot points for the measurements on a graph of time (x axis) against temp (y axis).
• step 7:


  draw 1 straight line of best fit from 0 min to 3 min and a 2nd one from 5 min to 10 min.
• step 8:


  connect both lines of best fit to the 4th min on graph and read off 2 temps at the 4th min from y axis.
• how do we work out the max temp change?

  finial temp - initial temp.
• what do we use the temp change to work out?

  energy change and molar enthalpy change.