H for each reaction studied will be calculated in units of kJmol of NaOH As

# H for each reaction studied will be calculated in

This preview shows page 7 - 11 out of 11 pages.

H for each reaction studied will be calculated in units of kJ/mol of NaOH. As discussed in the “Introduction” section the Δ H for the reaction is identical to the heat flow or “q” for the reaction since the reactions are being conducted at constant pressure conditions. In general: q = mass × specific heat × Δ T Since all the reactions in this experiment are being conducted in an aqueous medium, the specific heat will be assumed to be the same as the specific heat of water, which is 4.18 Joules gram ! C . The heat changes in this experiment involve three different components: 1) the chemical reaction 2) the aqueous medium and 3) the calorimeter. q reaction + q water + q calorimeter = 0 q reaction = -(q water + q calorimeter) A second assumption that will be made is that q calorimeter is negligible and therefore can be ignored from these calculations. Therefore: q reaction = -q water = -(mass water × specific heat water × Δ T water ) A third assumption that will be made in these calculations is that the density of the solution is the same as the density of water, which is 1.00 grams/mL. Therefore the mass of the water in each reaction is the same as the volume of the water. A fourth assumption that will be made in these calculations is that when combining solutions the total final volume is the same as the sum of the volumes of the individual solutions. 8 R EACTION 1 Mass of water = __________________ grams Δ T = T f – T i = ______________________°C Specific heat = 4.18 Joules gram ! C q water (Joules) = q water (kJ) = Moles of NaOH = q water (kJ/mol) = q reaction (kJ/mol) = _________________________________ = Δ H 1 R EACTION 2 Mass of water = __________________ grams (remember to include the ~ 2 grams of solid NaOH) Δ T = T f – T i = ______________________°C Specific heat = 4.18 Joules gram ! C q water (Joules) = q water (kJ) = Moles of NaOH = Moles of HCl = q water (kJ/mol) = q reaction (kJ/mol) = _________________________________ = Δ H 2 9 R EACTION 3 Mass of water = __________________ grams Δ T = T f – T i = ______________________°C Specific heat = 4.18 Joules gram ! C q water (Joules) = q water (kJ) = Moles of NaOH = Moles of HCl = q water (kJ/mol) = q reaction (kJ/mol) = _________________________________ = Δ H 3 E VALUATING THE VALIDITY OF H ESS S LAW Measured value of Δ H for Reaction 3 = ______________________ (same as Δ H 3 above) Value of Δ H for Reaction 3 based on Hess’s law = Δ H 2 Δ H 1 = _____________________ Percent error in the calculated value compared to the measured value: (show calculation below) Also write equations to show how reactions 1 and 2 will be combined to obtain reaction 3: 10 R EACTION 4 ( SAME AS R EACTION 1) Mass of water = __________________ grams Δ T = T f – T i = ______________________°C Specific heat = 4.18 Joules gram ! C q water (Joules) = q water (kJ) = Moles of NaOH = q water (kJ/mol) = q reaction (kJ/mol) = _________________________________ = Δ H 4 R EACTION 5 Mass of water = __________________ grams (remember to include the ~ 2 grams of solid NaOH) Δ T = T f – T i = ______________________°C Specific heat = 4.18 Joules gram ! C q water (Joules) = q water (kJ) = Moles of NaOH = Moles of CH 3 COOH = q water (kJ/mol) = q reaction (kJ/mol) = _________________________________ = Δ H 5 11 R EACTION 6 #### You've reached the end of your free preview.

Want to read all 11 pages?

• Winter '10
• Fisher
• • • 